If you haven't read book marketing expert Warren Whitlock's blog post on the three stages of Twitter, I recommend you read it now (see link below).
Whitlock, who is the co-author with Deborah Micek of the excellent book "Twitter Revolution," has written the wisest brief answer that I know of for people who denigrate Twitter. (Note these are usually people who are not actively participating on Twitter or even on Twitter at all.)
Here is what Whitlock wrote:
Most people go through 3 stages...
Published on February 24, 2010 11:01