Sniper don't Twitter?

One of the feature I built into JoyBidder eBay Auction Sniper is sending direct SMS message to bidder's Twitter ID when an auction is outbid or the sniper price is less than the minimum bid price. To enable this feature is easy, just have your Twitter ID follow http://twitter.com/joybidder. I thought it would be a useful feature, considering other sniper software (online or standalone) only send email alert. (To be accurate, there is one software does send SMS alert, but you need to install Skype and purchase Skype credit).

Here is the screen capture on configuring JoyBidder to sent alert via Twitter.

Almost 2 months after the feature was released, to my surprise, the reception is not what I expected at all. Only a few users have tried, even they don't use that much.

Why is it, could it be of the following reasons?

1. Most of the eBay users don't have Twitter ID?
2. You don't want others to know that your Twitter ID is following joybidder?
3. SMS outbid alert is not useful, since if you are not near your computer, you really cannot do anything with it.

What do you think?