Monitoring what people are doing as they interact on your websites is one thing. Launching a chat application to talk to them as they browse is quite another.
The implications are pretty huge, you know that they arrived at the site by searching for “blue widgets” so you can ask them if they found what they are looking for and direct them to the right page if they are having trouble with the search form. The only problem is do people like to be watched in this way?
I know that webmasters can watch my every move online but most people think that browsing the web is a fairly anonymous affair.
As Arrington says in the comments: “Someone opens up a chat window on me while I’m visiting a website, I never come back.”