Better than me, I got up to 42 and still debating if I should finish it. My on hold list could be considered dropped since some I started long ago and just haven't been feeling like watching any of them. People have to urge me to finish :/ that's how I got through Secret Garden.
yea, i'm stalled out on Lee Soon Shin too.
the latest i dropped is prime minister and i, i just couldn't get through the 5th ep !! it's too boring and i just couldn't feel the chemistry nor the story :/
the last time i dropped something was a really long time ago. Love Rain and She Is Wow.
I just cleaned out my On Hold list and dropped: Innocent Man-I just can't, it's not the acting, its a drama that I can't enjoy, way to sad and upsetting. Also, its been sitting On Hold for almost 2 years now. Love Rain-I really liked it in the beginning, and then I just sort of fell out of watching drama's, and this got stuck. The King of Drama's-I don't even know what to say.. I found parts of it to be funny, but the arrogance of SiWon put me off watching this. The Master's Sun-Please don't kill me... I watched one episode, and in that one episode, I could see the whole drama unravel.. so nope not for me... Other than those I recently dropped Boys on the Run.
The ones I've listed as dropped (I have plenty more) are these: Hello my teacher. Gong Yoo was not believable as a student, and the show was just silly. Not funny silly, just why am I watching this-silly. Boys on the run. I only tried to watch this because I was curious about Ueda's acting, and his role was interesting. However, rest of the show was not, and since he didn't get much screen-time, I gave up. Faith. I'm not that big on time travelling in the first place, and this had an annoying female-lead and nothing interesting going on. I just wasn't able to focus on the show at all. Honey and Clover. I've tried it. I've tried the manga, the anime, and now the drama, and I just can't. I simply dislike the idea of it. It has great actors and I wanted to be able to watch it to the end, but fact still is: love triangles. I hate them, and this show is way too full of them. Love Rain. I'm just not into the whole flashbacks to some old love-thing, I got enough of that watching some other series. So even though this could've been really good, I got annoyed. Nihonjin no Shiranai Nihongo. I don't even remember what this is....... Que Sera, Sera. Started out great, I loved the main-female which is very rare of me, it just looked like it was going to be great. Then things happened, it went bad, I had to quit. I just checked spoilers on what was going to happen in the last episode to give me closure. Stand Up. Again, great actors, but I just can't focus. Not enough going on to interest me. Sweet 18. Hahahahahhaha oh gods. So dull, so bad, so nope. I can't believe it took me so long before I dropped it. So basically my reasoning to all is either: I don't like the plot, or majority of things are too boring to keep me focused on it.
Family's Honor. I love Park Shi Hoo but the family was the most dysfunctional one ever and I couldn't take that past the 6th episode.
I've only officially Dropped one drama (and one movie), although I've had plenty that I probably should have dropped.

Heartstrings: The middle of Episode 14, I set down the remote and walked away. I found this drama to be incredibly boring. Anytime something remotely interesting occurred they quickly squelched it. The two leads (who I liked in You're Beautiful) Just never seemed to really get that spark.

I keep thinking I might finish this drama but no it's been a year, I"m not.
I dropped 98 dramas, so impossible to list the reasons to all, some I tried to start them again and again and always stop at the same episodes, like Secret Garden, Summer Scent, The moon that embraces the sun, Sweet spy, and I always get bored. Some I dropped but I still read the recaps, and with some even stopped with the recaps. When I find myself fast forwarding the episodes or put pause and go do something else, and I go back and hit "close window" then it's time for me to drop that drama.
The most recent one I dropped was "I Need Romance 3". The main lead is annoying and on top of that I was bored to tears. Mianhe NGM! I keep dropping the dramas you are in. LOL
The latest drama I dropped was Reply 1994. I liked its predecessor, Reply 1997, a LOT. But for some reasons I could never get into 1994....
Boss and Me... .... .... I have been working on my tolerance, this broke it. It was almost like watching the "chaste" version of 50 Shades of Grey... No thanks!
Most of my dramas go on the "On-Hold" list before making it to my dropped list. Part of the reason is because sometimes I just start too many different dramas at once and get bored with all of them, or sometimes I'm just not feeling them at the moment. I go through the list every now and then and question myself "Am I really going to get back to this?" If the answer is probably not, then I drop it. There are a few that made it to the "Dropped" list without being put on hold first though.

49 Days - I sort of guessed how this one would end and then I went to confirm it before finishing. I was partly right. What I was right with I was okay with, what I was wrong with just sort of annoyed me.

Love Rain - It seemed to me that many people seemed to like the beginning of it, however, I was just overall annoyed with most of the characters (expect one and I just ended up feeling sorry for her and she wasn't even the lead). However I patiently sat through it and thought "hey maybe I'll like the second part of it better..." Nope.

The Heirs - I couldn't even sit through the entire first episode. I just really wished someone would slap the female lead. I'm usually okay with female leads who aren't stereotypical "Candy Girls", however, she took brat to whole different level.

Lastly, Queen In Hyun's Man - Usually, I try to get through the first four episodes before making a final decision on a drama. I had to force myself to get through the second episode, it was just incredibly boring to me.
I have more than a few. I'm picky. Here are the most notable: 

Greatest Marriage/Best Wedding - Unable to make it through this one. I loved No Minwoo in Pasta, but his overacting in GM did me in. He needs to dial it down a notch.

Mary Stayed Out All Night - Didn't love it, didn't hate it. Just blah. I couldn't be bothered to finish it because by the time I reached the last few episodes I just didn't care what happened to any of the main characters.

Rooftop Prince (I KNOW) - I dropped it around episode 10 because I was only watching for the Red, Green, and Yellow Rangers at that point. They were pure comedy, but other than them I was bored silly.

The Girl Who Sees Scents - I couldn't really get into this one. I liked the premise and I like Yoochun, but I can't get past the fact that I find the lead actress super annoying. Also, although it's probably purely cultural, the stand up comedy aspect wasn't funny to me...like, at all.
Hanzawa Naoki- I didn't understand pi about it. I reached the second half with a lot of black holes in my mind, I couldn't put the story together so I dropped it. I mean it was good, excellent drama in so many ways but I think bank stuff is not something my mind easily understands. *so ashamed*

Mary Stayed Out All Night- I remember I reached an episode where I just said "Why are you rejecting the rich/perfect boy and staying with the worthless and very feminine poor guy."  Jang Geun Suk cared more about his hair and looks than putting up a great performance. It was so much disappointment.