Blocking is cheap.

doing anything more than once per 5 seconds

In the case of throwing fireballs, there's a good chance it's not spam. The ones you claim are spam should be the ones you can get around easily. If you're getting out-zoned, and you're baited to make un-safe jumping attacks, that's not spam. He's out playing you. A lot of times good zoning from Sagat or Ryu can be a barrage of fireballs, especially at that perfect spacing. You're forced into an uncomfortable position with little room to work. That's sort of the idea though. 
 
This topic is now flamebait, so I'm going to go ahead and lock it.