I agree, Twitter is awesome. But I think Twitter is more useful as a passive conversation tool. As in, okay here are the 100 people I like and following and there's no direct pressure to care what about everything that they say or engage with what they say. But if I do, wow, it's pretty addictive. Like an IRC chat with constant flow but without the need to pay quite as much attention.

If his goal is to use it just as a broadcast medium to promote his projects, a la @barackobama, then that's useful but in the grand scheme of things wouldn't he better off going on TV? By being on Twitter, the PR get is for Twitter. The novelty is the fact that someone like Al Gore is messing around with something that many people have been discounting as just a toy for the past year (even though I've heard the market values it to be quite a pricey toy).

As for the s/n ratio, it's manageable but for people (public figures, Kevin Rose, iJustine, etc.) that have thousands upon thousands of followers it becomes outright ridiculous. They don't even bother responding and I believe it just defeats the purpose.

If someone like Al Gore wants to help I really hope he starts engaging in more conversations with regular people, because that's really a good thing. Twitter is an avenue that he can pursue but again... the s/n is so out of whack without advanced management and plus the 140 char limitation it might just be counter-productive. But hey, right track and everything!

I follow a few people that have many thousands of followers. They often reply to my @replies. It isn't something you can constantly do, but it is an important sign of authenticity that they do so periodically.

Authenticity is going to become increasing important for people with personal brands, like Al Gore.