I noticed this note on their homepage today:
Thursday, August 4th, 2011
From the desk of Tom Williams, operator of MyBitcoin.com
For immediate release.
As you have probably noticed, MyBitcoin.com had been down for almost a week due to an unfortunate event.
On Friday of last week we noticed that one of our pooled holding servers was missing a large amount of Bitcoins. After a prompt investigation we realized that the security of our SCI (Shopping Cart Interface) system had been breached by an unknown attacker.
Our response was rash, but necessary. We simply switched the system off until we could have system-wide forensics performed. The forensics took some time, as the system is quite complex by nature.
After weighing all of our options, we have realized that we have no option but to go into receivership. We will settle all accounts with a online claim process that we are currently in the process of working out.
We will release more detailed information about the security breach, the claim process, and our balance sheet in the next few days.