1. Aquihiring may be cheaper then new hires overall, considering externalities. 2. The underlying tech may be useful. 3. The user base may be acquired. 4. the business relationships may be retained if they are beneficial. 5. Potentially less competition in a market.
Pinterest is burning through enormous amounts of VC money.[0]
Betaworks seems to just be selling its Instapaper product, together with the Instapaper team.
Thus I'm guessing Pinterest needed a crew that could do what the Instapaper crew can do, and was willing to pay a lot more for it than it was worth to Betaworks.
I can totally see where that could be worth it to Pinterest. Talent is in short supply. Their revenue per engineer is probably not a good (nor available) metric but I bet their burn rate per engineer matters, and their "VCs are Impressed By That" per engineer is probably a huge deal for them.
Hopefully that crew is getting proper relocation packages.
(Or, of course, I'm totally wrong about everything. I don't actually use Pinterest, because it's too visitor-hostile.)
Oh and too bad about Instaparser, I thought that was the most interesting thing Instapaper had done yet. I'm sure somebody at Pinterest came up with a number for what it would cost to build that internally, and that number was probably close to the purchase price.