I'm not exactly one to gripe as a couple of years ago I took a new job and overloaded my schedule. I thought it would allow me more WIS time, but it actually allowed me less. I ended up getting the bump from several leagues -- including one I was running -- because of how little I was able to do on the site. I always had enough time to check my sitemails, but not always enough time to reply to all of them. I felt horrible about it (and still do), and honestly thought I would be able to keep up with all of my league commitments even though it was obvious I couldn't. My teams were also suffering as I didn't have time to keep up with most of them, so I started losing alot with a number of teams and getting poor picks as I was often late in making picks and didn't have the time to research enough to even compile a proxy list, let alone send the list to someone. Getting the boot from my own league was my wake up call and I cut back from 18 leagues to 4... about 4-6 of those leagues I was dropped from by the commissioner before I had the opportunity to resign myself.
For that reason, as well as for the reasons others have mentioned above, I try to be real slow to call someone out, but I do have a handful of names on my list that I'd be cautious about before allowing into one of my leagues (as in, I'd probably sitemail them my expectations and let them know up front that if there is any suspicious behavior that leads me to believe they will do as I've always seen them do, that I will have them removed from the league, even if it's mid-season):
bradsldunn/blues322 - He's done much better since being called out under his bradsldunn name and using his new name of blues322, but I still don't know if the two teams I saw him run under bradsldunn were with malicious intent or if he was just that naive about running a team when he first started in progressives. I took over one team of his in the davkar progressive that had seen him trade away all of the future talent and all of the 1st 3 picks in each of the current draft and the next season's draft (in just the first 2 seasons of the leagues existence). When I got the team, even after drafting 6 players -- and making two quality for quantity trades before the season started -- I only had 532 IP and 3800 PA. It took me 4 seasons of drafting quantity before I got to a respectable 1200/4800 level. The same was true of a team I saw him run to the ground an trade the picks away from for an attempt at one season glory before he left that league, too (I don't remember the name of that league, sorry).
The two above may be the same person and I haven't been in a league with either of them in awhile. I doubt it's malicious, I think they honestly try to win, maybe... I've defended them a few times in different league forums, but then, I've also had them removed from one of my leagues mid-season by having admin transfer it to me. They usually stick around for 5+ seasons and give good notice before leaving, they just leave every team in shambles. (I was in 4 leagues with them).