Google's business model
First they slurp Waze, then they slurp the data of Waze's users. As a (infrequent) Waze user I don't like the deal at all.
On the other hand I don't see how the FTC could stop them. There are still several players in mobile navigation, so there is no imminent danger that Google could become monopolist at this moment.
What will happen is that many users will abandon Waze for other less Googly navigation software. I suppose Google took that into account when they decided to take over. Otherwise they might be in for a bad surprise. That's market at work, isn't it?