[Cthulhu_]

Locking files in SVN so other people can't edit them until you've unlocked it again.

I've never seen it used, and the only references I can think of was where it was just annoying, if not a risk (someone locking a file then leaving over the weekend or the company entirely).

[PudgePacket]

I've seen it used in games. Often serialised assets won't be text diff friendly. Two people editing the same data will conflict and it won't be possible to merge the result. The solution is only one person checks out the file at a time.