I wouldn't expect them to buy hardware, but I definitely could see them going to a dedicated hosting service like Softlayer (where you still just pay monthly and can usually bring up more capacity fairly fast, but you get whole machines instead of virtualized machines).

It seems like that would make a lot more sense for Reddit, since I/O is so slow and flakey on EC2 (from what I hear), and it's not like they're really taking full advantage of the elasticity that EC2 provides (by massively scaling up and down to fit major load variance)