I don't understand why people think increasing their usage shouldn't cost them more. These plans are all designed with an expected usage in mind.
3G isn't really that slow - light browsing and things like Pandora make hitting 5 gigs pretty darn tough. But if it's faster people will shift usage from PC's, some even talking about dropping home broadband or tethering = saving money and then whine that the might be capped by VZW.
Probably 98% of users don't hit 5 gigs a month now, so faster shouldn't change you're usage unless you shift you're usage. Basic supply and demand says you should pay more for that.
If I'm VZW and have the capacity, this being a viable alternative to many for home broadband means there's some $50 a month they can capture in additional revenues from tethering. They can cap at 5 gigs and then, if you want to replace home broadband with tether, can charge $30-$40 more for unlimited and everyone wins.
I think where it becomes an issue is when mobile sites take advantage of increased speeds to deliver more data-rich content which increases data for the same given usage pattern.