Re: You're thinking too hard
You think because some acquisitions, like Motorola, or the Rockstar consortium's buy of Nortel's patents were for patents that all are? It is hard to see Nest being worth $3.2 billion based on patents (well, it is hard to see it being worth $3.2 billion by any measure, I guess)
Sometimes companies acquire another because they plan to use their technology. It is a lot easier to see where Google might use the type of stuff DeepMind is working on to improve their core search technology by making it better able to know what it is you're actually looking for when doing a search. DeepMind may not even have any patents, some companies operate more in terms of trade secrets - as Google does for its latest versions of search software which are not covered by patents.
Similarly, when Apple buys SnappyLabs they're probably buying it to integrate into iOS, not because Apple wants to try to fight others based on camera patents.