Ask HN: Examples of successful startups done by software houses?

Two Toasters did the airbnb apps.

http://thenextweb.com/apps/2012/11/18/from-ios-to-android/

Given how many of these app development shops there are out there, it's surprising that one of them hasn't hit a home run.

There's probably something inherent in the people, structure, and incentives that prevents it from happening.

You mean: company A has an idea, they go to company B to implement it? What about ranker.com?

Yes.

I think alot of it depends on how the deal is structured. If the software house doesn't have ownership in the final product, then the incentives just aren't going to line up and the product will suffer.

You have some Startup Studios with some success.

Check http://buildtogether.co/ 'Everything about Startup Studios'

slack by metalab is a great example imo.

Tinder comes to mind.

Wasn't Tinder done by IAC owned incubator, not a 3rd party software house?

fog creek / trello

I'm not sure if this counts. Fog creek owns Trello.