Distributed Version Control
A couple of very good and interesting posts covering Distributed Version Control and version control thoughts in general. Both have some very good discussion and the comments are well worth a read.
The Risks of Distributed Version Control - Discusses a potential "community" problem with distributed version control systems (such as git, mercurial, etc.) where people "go away", work on something by themselves and then return with a huge mass of code. Not a technical/tool problem, but a group dynamics issue.
Version Control and "the 80%" and its companion follow-up Version Control and the... Long Gradated Scale