i think it will become inevitable. as yc increases its number of investments, there will be more companies doing similar things and competing. i think the ethos of yc is to prefer a partnership (or downright acquisition) over competition, as most times, you have other competitors, and you can find ways to team up and take on the big guys. why not work with the same people who went through the same seed fund as you? the real question is: at what point is it acceptable to merge or get acquired?

paypal and x.com were a great example of what can happen through a merger. they could have spent their time killing each other, but they merged and set their focus on much bigger things: taking advantage of ebay's mismanagement and poor execution to deliver the world's leading online payment platform.

private acquisitions seem strange, but i have always believed that the real reason large companies cannot form from start-ups is because people may be too resistant to team up with their leading competitors to take on an even larger competitor. i wonder what would become of microsoft had they not teamed up with ibm, or apple.