[robocop]

I don't think this approach would scale, due to the time investment required. It also suffers from making it hard to compare one candidate to another in a fair way, unless you have everyone fix the same bugs. Having a bunch of canned bugs to be fixed doesn't seem much better than asking a CS puzzle.

[Evbn]

I Lways ask people to slave a simplified version of an actual problem I have worked on recently. Some times I even learn some thing.

Comparing candidates is irrelevant. You just want N hires that can contribute in your environment.