Another rule of thumb I use which would apply to companies like Chilihost
who may already have programmers on staff:

If it's stupid simple, build it yourself because you can build it faster than
you can Google it.
If it takes more than 15 minutes to write - get it from CPAN if you can and get
quality code in less time than it takes to write.


I had to edit this post because I first typed "who already have programmers
on stuff" - I've seen a lot of code which looked like it was written by
programmers on stuff.