microsoft did it pretty easily, albeit 4 years later than amazon, which is partially why they're playing catch up. microsoft didn't have any "industrial warehouse buying" expertise and was a lot more familiar with server tech than amazon was at the time they started aws in 2006, and probably had a good number of data centers already, they just weren't built for rental services.

although it's outside facebooks current core competency i think they wouldn't have too many issues getting into the cloud game if they wanted to. they could hire all the expertise they need and get 100 data centers up and running in 5 years.

but why would they? it's like google getting into the ISP market to compete with verizon et al. google runs its very profitable business on top of the commodity rails and keeps limited deployments of google fiber as a stick to threaten slow or uncooperative ISPs. facebook can run its profitable software based businesses on top of the infrastructure instead of joining the cutthroat race to the bottom of cloud computing that may or may not be semi nationalized/regulated as ISPs and utilities are today