I've walked through a couple of different tutorials and now have more than one "sandbox" account. I asked a question over on Stack Overflow about whether this was a problem (or if there would be a problem if I _merged_ multiple accounts into one).
Right now, though, I'm also wondering about the phone numbers automatically assigned to these accounts. Are these numbers persistent? Are they exclusive? Is there a problem if I accrue multiple numbers, or are they reused for other sandbox apps as well?