Still has all the problems that counting citations do: how do you count multiple-author papers (particle physics has given up ranking authors and just put the hundreds of authors in alphabetical order, IIRC) and it encourages people to write piecemeal papers, because why say something in one paper if you can say it in two -- and get twice the citations?
Also, my favorite: What if you cite someone to say that they were completely wrong when they approached the same problem? Should that be counted as a positive for them?
Presumably, no one is going to try to prove something wrong that has already been proven wrong, so unless there are many obscure flaws in one's work that take multiple papers to uncover, it shouldn't affect the citation count much.
In introductions, papers often give a short overview of what's been done before, so early work in a field often gets cited even if it turns out to have been flawed. (It can't be completely ridiculous, of course, it must have sounded plausible at the time, but even shoddy research often does.)
Also, my favorite: What if you cite someone to say that they were completely wrong when they approached the same problem? Should that be counted as a positive for them?