I've been weighing every day lately... because I'm so excited about my primal food. haha. Before (while trying to lose weight) I was weighing once a week. Before that, I almost never stepped on the scale... and somehow gained about 20 pounds in 2 years.
So, yeah, I think it's good to step on the scale now and then just to keep track of where I am (and don't wake up 20 pounds heavier...again). More than that is fine as long as it's not becoming an obsession. I'm sure once I settle into my primal diet more I'll weigh less often, but for now it's just so fun.