Join Twitter. Five minutes later, post your website and ask your zero followers to look at it. Wait. Publicly send a Hi Howyadoin' to a celebrity. Mention your website, maybe the celebrity will feature it on their TV show. You'll make millions.
OK, if you're done laughing, here's the reality of it.
Nobody on Twitter cares about anyone else, least of all you, unless they know who you are and like you. If you walk into a packed movie theater 20 minutes before the show, and announce that you're selling anything other than discount popcorn, the best result is that everyone ignores you. The analogy fits because you're unknown to 300+ people who are gathered for a different purpose.
Twist the analogy:
Oprah Winfrey walks into the theater and has a book in her hands while she waits. She doesn't even have to say anything, and 5 people will go buy the book. She has celebrity status, credibility. If she were to wave the book in the air and say, "buy my new book," 20 more would go buy it. 100 would think she's blatantly marketing and 175 would never even notice her simply because they still only care about the friends they're with.
Treat Twitter, Facebook, and Myspace like they were originally intended: Friends, family, coworkers with a common interest. This is not your public, cold-market, marketing vehicle. This is where among your normal conversation you may discuss your product of value to an individual or small group; if others overhear, they may join in but only if they're interested. Even if you were to mention your love of chocolate 15 times in a day, people would get irritated. Keep product mentions to a minimum, and if more than a couple (1%) of your followers speak up against you, assume the 99% that didn't, are offended - and back off.