Do big internet companies get with with DOS attacks?

I’ve read a couple articles about hackers extorting money from various sites by threatening them with DOS or DDOS attacks, but even though those sites appear to be big in their industries, I haven’t heard a story about a company like Amazon, Yahoo! or Microsoft being hit with those.

I wonder if this ever happens and they just have the resources to deal with it until it goes away, if they keep it quiet or it just doesn’t happen.

It looks like it happened to yahoo