Yoshi said on lftp live that those were employees. He wanted the ingame to look lively. It's not like the developers are home with their families at 20:00 these days.

For alpha, you logged on with your SQEX ID to apply to participate. Your forum account is bound to your SQEX ID. You post anything about the alpha, you're kicked from it. The agreement is typical and strict and within SE run forums, a poster can be tracked to their accounts, removed from alpha, excluded from beta.