Are social sites such as Facebook and Twitter CPU or IO bound?
I'm coming at this from a Node.js perspective where the general consensus seems to be that it shines for IO bound use cases.  I'm not trying to build the next Facebook/Twitter but my question is are social networking sites generally I/O bound or CPU bound?  Since social networking can encompass such a wide variety of contexts, I will further specify that I am specifically interested in functions such as chatting, instant messaging, following users and status updates.  For these types of things do bottlenecks generally occur on the CPU or IO side?
Are social sites such as Facebook and Twitter CPU or IO bound?
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I'm coming at this from a Node.js perspective where the general consensus seems to be that it shines for IO bound use cases.  I'm not trying to build the next Facebook/Twitter but my question is are social networking sites generally I/O bound or CPU bound?  Since social networking can encompass such a wide variety of contexts, I will further specify that I am specifically interested in functions such as chatting, instant messaging, following users and status updates.  For these types of things do bottlenecks generally occur on the CPU or IO side?