Yeah, that's my #1 gripe about Google Voice. The service itself is pretty essential for me, given that I have to keep my cell phone in a locker outside our office suite all day. But, now that I've given everyone my GV number, I have to then tell them that whenever they send me an MMS, to send it to my mobile number. Of course, they think my GV number *is* my mobile number, so then they end up changing my mobile number and not sending to my GV number anymore, defeating the purpose of having it in the first place.

I don't know enough about how GV works to know if it's an easy fix or not, but it's really annoying.