This correction has been coming for some time now. I think the Mybitcoin incident is just a coincidence.
I think it makes sense. People have been getting a bit scared about how to store their coins. On their PC they could be snatched by trojans, web services snatch the coins for themselves or simply disappear the wallet, and so on. So they sell them...
We really need to make it easier for mainstream folk to secure part of their wallets. Yes, there are a lot of proposals for this, but it'll take some time for trust to be restored.