> What possible reason could Facebook have to purchase a company so far removed from its core competency?

I would imagine Facebook feels under pressure to build up a core hardware engineering team. It's pretty clear that embedded and wearable computing is going to be a huge industry at some point in the future, and Facebook is going to need to get into that industry unless it wants to be indebted to and reliant upon hardware manufacturers.

So really, this acquisition makes sense for the same kind of reasons Google acquiring Nest makes sense - neither company has strong expertise or experience in consumer electronics hardware, and they need it going forward.