When you branch some code, finish working with the branch, and merge it back to the trunk, what do you do with the branch? Delete it from the repository? Keep it for reference?
It seems like you would keep it for reference, but I imagine the /branches directory could get pretty cluttered.
(If this isn’t something people generally agree on, please comment and I’ll make it a community wiki.)
Clarification
jleedev is right – we should specify which version control system we’re talking about.
I had Subversion in mind, but would love to hear responses regarding other systems, too. Please specify which one you’re answering about, or, <bribery>if you want to get the accepted answer</bribery>, compare and contrast several systems.
I remove reintegrated branches since I do not need them any more. Git and Mercurial keep branching/merging history anyway. In subversion I’d keep old branches to have a reference to commit history.