Apply a no-exceptions whitelist to your email and you'd have the same thing. Almost nobody does, this, though, and for good reason.
This guy is absolutely right that Twitter is a clever design that folks would be wise to learn from. But Twitter doesn't so much eliminate the problem of spam as dodge it: most people still need a way for relative strangers to get through to them, but they have email for that, so Twitter doesn't need to solve that problem.
If email ceased to exist, Twitter might find themselves pressured to reinvent it, and then spam would arrive right along with it. Similarly, if Twitter yielded to pressure to create a forum like this one, where relative strangers can contribute to discussions, trolls would arrive right along with that feature.
I think there are similarities between Facebook and Twitter in that the networks that form are localized within groups of individuals that are familiar with each other. Facebook originally did not have a spam problem up until they themselves decided to spam their users in an effort to monetize their traffic.
Twitter, if it is to be profitable through advertising, will have "spam" in the form of advertisements from within Twitter the same way Facebook has various forms of spam from within (Facebook apps included!).
Nonetheless, 1 million users along with the claim of the article is impressive at this point. I don't use Twitter (how un-2007/2008 of me no doubt) so I cannot comment on getting spam.
This guy is absolutely right that Twitter is a clever design that folks would be wise to learn from. But Twitter doesn't so much eliminate the problem of spam as dodge it: most people still need a way for relative strangers to get through to them, but they have email for that, so Twitter doesn't need to solve that problem.
If email ceased to exist, Twitter might find themselves pressured to reinvent it, and then spam would arrive right along with it. Similarly, if Twitter yielded to pressure to create a forum like this one, where relative strangers can contribute to discussions, trolls would arrive right along with that feature.