ronin - 4:09 pm on Mar 18, 2010 (gmt 0)
SMS is (normally) one-to-one.
RSS is one-to-many.
Twitter is one-to-many + many-to-one + one-to-one.
Twitter is RSS with feedback functionality - it is to RSS what articles with comment functionality are to traditional comment-less articles.
That's the platform. What people use it for is another issue entirely. If you're going to blame Twitter for meaningless spam, you might as well blame the W3C for scraper sites.
The great thing about twitter - as with RSS, but UNLIKE email - is that the moment you receive any spam at all, you can switch it off with one click.