I just managed to get two bitcoins sent to my wallet at mybitcoin last night and I was expecting to check on them this morning. If the site never comes back up am I just SOL on those two coins lost in transaction?
If the site never comes back, then you've lost your coins.
"mybitcoin.com" is effectively the same as giving someone else your wallet.
Not a good idea. I also recommend against using services such as "dropbox" for storing wallets.