Never heard of anything like that. I did transactions the instant I signed up on MB.
Same here.
I didn't say anything, because I haven't done anything with them in over a year and I signed up to the service several years ago. I do remember that when I signed up, I sold a WoW Account and the money was in my real bank account within a week of signing up.
I did some searching after the first reply, but I couldn't find anything about them holding money for 30days.