Other time zones and that makes communication difficult, so no quick IM with "by the end of the day" as that means something different over there. Different culture and way of doing things, so have to spend a lot more effort in communication being very clear. Even then they're far away where it's a lot easier to hide stuff until the hole is very deep. Travel expenses going up very quickly for a little training for a new guy. It can be so fun to work with teams in a different continent.