Why wouldn't you sign up? - Need feedback for MyTweetAlerts

I saw this thread from @awhite and would like to try something similar.

I need brutal honest feedback about my startup https://www.MyTweetAlerts.com - it is a new and better way to search Twitter. Email alerts for Twitter.

Why would you not sign up?
Would you pay for such a service - why - why not?
Do you understand what the website is about?