Well in the pre-uigea days Neteller was the company winning th transfer market.. very similar to paypal except you could use them for poker sites.
When the UIGEA passed, neteller had all it's assests frozen.
This is common practice though.. poker players will have a huge chunk of their networth on poker sites. Keeping money online just made sense, that's where you would use it to make more money.
So I didn't get it locked up from a poker site itself (as far as I know no one lost money that way), but from the payment processor. Everyone got their money back, it was just a long time.
I had a couple months worth of living expenses (I was small time).. but others had dozens to hundreds of 1000's locked up.