I don't think it has anything to do with Googles algorithm. Over the years, I've had various browser plugins to hide EE results from my searches. Various upgrades meant I had to find new plugins every 10 months or so.
Now it's easy for everyone. I hit the 'remove Experts Exchange from search results' button the first time I saw it.
I hope Google is using remove from search results as a signal in their ranking. I think it's a fair way to weight.