Hey Jonathan,
There isn't anything in factory_girl that references curl, so it has to be something in one of your factories, your models, or something else your application depends on.
If it doesn't happen locally but it happens on another server, it sounds like an environment different. If something is actually making a curl call, it's probably because the URL doesn't generate correctly in other environments.
It's hard to say more without seeing the code, but I'd start looking through your models to see which one is calling curl. Looking at the full backtrace (try rspec -b) should help you find it.
-Joe