Linked Steam Accounts Not Affected By PSN Security Breach

Steam Accounts Not Affected!

"Steam has nothing to do with the PSN outage." - Steam

As the above link states, Steam isn't involved in any way with the PSN issue. Therefore, if your Steam account was linked to your PSN account such as through Portal 2, your Steam account isn't compromised or anything.  So on the bright side of everything, you don't need to worry about your Steam account.