Sure -- while they were gaining critical mass they were happy to pay Google's fees. Now they're big enough that they feel they don't need to anymore.

This goes back to what I was saying about whether or not a business should be owed some kind of 'gratitude' over past actions. There's no rule in a capitalist system that says you owe someone continued patronage just because they used to provide you with a good service.

It's all about what value Google is providing right now -- the past benefits are irrelevant.