As I sit and look at the replies already coming in, may I just add an enormous [citation needed] to the entire discussion? A question brought on by too many conflicting anecdotes can not be resolved by throwing another unsourced anecdote on the pile.
(Incidentally, I'm at least a bit curious myself as to the answer, and have my own pile of conflicting anecdotes I've read.)
Statistics and citations today is the Bible quotes / racial stereotypes of yesteryear. Some modern-day pseudo-scientist poster will cite some study that says "80% of chargers waste power if left plugged in at 100% charge" will then draw the logically faulty conclusion that therefore you should unplug your charger. The fact that the statistic study necessary had to ignore extra variables like if you have a lot of stuff plugged in, whether you're drawing power from a set of solar panels on your roof, whether you are using a super-special non-power wasting adapter, etc., necessarily makes the citation not a thought more credible than your great-great grandpa quoting the bible to tell you that you should marry your own race or citing stereotypes that you shouldn't trust your friend because he is Asian.
True science, that is, proposing hypothetical models, analyzing results, and admitting no real results can be drawn due to insufficient model complexity, has been thrown out the window by pride and laziness.
The question is simply "what do we know about this problem" not "what is the absolute unquestionable universal answer."
Also your comment has some interesting points but starting off by comparing statistics and citations to bible quotes and racial stereotypes isn't going to win you much support.
It's difficult to argue the idea that any manufacturer of a device containing a battery cell would not engineer the system for the proper balance of longevity, capacity, and durability to result in acceptable quality to customers.
If I were running a social network like this, I'd post questions with definitive answers like this one, see who voted up / wrote the wrong answers, and then block those people from voting / commenting again for a long time period.
Do that enough times, and you'd quickly have the smartest site on the Internet.
This thread literally has people posting links to Yahoo Answers.
(Incidentally, I'm at least a bit curious myself as to the answer, and have my own pile of conflicting anecdotes I've read.)