Big discussion about this topic a few days ago:

https://news.ycombinator.com/item?id=23929044 (1085 points/349 comments)

Why bother investing and prying when you can simply buy those companies off once they become large enough?

Cheaper to make a small investment, take everything you want and let the company fail. Simple economics.

That's true but on the other side, ideas are sold dime a dozen, only their successful implementation proves in hindsight that the idea was worth something. Stealing ideas doesn't mean much as they are available aplenty but a startup which successfully implemented that idea is worth something.

Ideas can be promising but implemented sub-optimally. Using this method, they get inside information on where things can be improved. Then they have the financial clout, the data analytics and the resources in place to create a successful final product.