You can if you want. It's about relative movement in weight against the same measure, not whatever the absolutely correct figure is.
However, you also want to have some form of accuracy. Don't wanna stop when you could still need to lose 10 more pounds, right?
Remember nobody sees your history but you, and you know what that blip is about. As for friend feed, if you're worried about that, just make a status about it.
Or you could just not weigh in again until another 10lbs lost so that it looks like you just maintained for a while instead of shot up 10.
Deb, in New Zealand