[nandemo]

If you buy a notepad, the paper manufacturer doesn't own it anymore and has no control over it.

Google cannot claim it doesn't have control over its own servers.

A more apt brick-and-mortars analogy would be a theater that would let anyone use its projector, as long as ads chosen by the theater are displayed alongside. Surely in most countries the theater would be liable for showing illegal movies, no matter what they'd written in their disclaimers.