These kids (I'm 30 now, I can totally pull off the crotchety old man thing) drink the cloud kool-aid and think "great, we don't need to think about our infrastructure". They slap together something that almost works, but is a management nightmare. It's no different from the startups I was consulting for in the '90s, except it's a lot quicker to use a brute-force scaling approach now.
I like S3 for what I use it for: cheap tertiary archival for ~20TB worth of backups. Beyond that though, it's hard to find ways for the numbers to work for the pure cloud hosting sites. Especially for services that are more than just simple CRUD apps. None of the startups I'm currently incubating can do more than maybe some simplistic web hosting there, since they all involve "complex" infrastructure needs. (I double-quote complex, because in my world, BGP route optimization or IPv4 anycast is just a run of the mill daily problem).
2Gbps is indeed a different ballpark. For most sites I have seen in that realm it would be ~90% static content (i.e. media). If your site truly needs to hit logic for each of these requests then yes, a distributed solution probably won't do there.
Anyways, I didn't mean to say that EC2 is the be-all for everything. I just wanted to place a counterpoint against that all too common, lighthearted cost-bashing which too often is not backed up by figures that make sense the way yours do.