It seems like they did a system wide audit this past few days to root out the heavy abusers. I use foursquare and don't exactly provide my actual identity unlike Facebook so people wouldn't know where I am at any particular time. Using four square is more private and to feed my check in addiction to get badges. If they really want to verify, they can check my other check ins. It's not like I am doing drive by check ins. I don't particularly agree with having to have receipt in order to get points but it's their program son they are allowed to do what they want. I got an email back just a moment ago that my access was restored. Sure enough, I was able to log in.