No, they haven't moved my coins since the since the site went down, but then again they didn't complete the withdrawal I requested from their system ~24 hours before the site went down. Unless we start getting reports that coins have been moved it would seem like negligence - not outright fraud/theft.

You may want to have a gander at these threads:
Mybitcoin.com, where did it go? - http://forum.bitcoin.org/index.php?topic=32984
mybitcoin down or just me - http://forum.bitcoin.org/index.php?topic=32900