I think it's a clever play.
It would help address the spyware concern by moving it to a US company, and give them a better foothold in Social Networking than Linked-in provides.
I'd have a few concerns about if MS can keep it growing-
For one, I worry that Microsoft may mismanage it, similar to how they treated Skype.
We saw Yahoo buy many reasonable smaller social networks (Flickr, Delicious, Tumblr) and was never able to make it work.
Microsoft has seemed to get better at acquisions lately though, so they may be able to pull it off.
The other concern is that youth-based social networks tend to have a short half-life; Snap isn't exactly taking over the world anymore.
But personally, I absolutely think it'd be worth the gamble.
The price is relatively low (just over 1 quarter of revenue), and if they can keep it going it's a good hedge against FB, if nothing else.