Google Alerts complement RSS for me. I like being able to get alerts for articles as they are posted online. Technically, you only get alerted if, Google (GoogleBot) has already crawled the web page.
Sometimes, it's quite cumbersome wading through the massive data that RSS mines, and might not to get that much needed information in realtime.
It would be useful for:
- Stock Market junkies and Security Enthusiasts: Getting the latest news on a company that you have positions on, or conducting information gathering tasks as part of a penetration test
- Sports fans: To get real time results of the sporting events that they like
- Journalists: News updates in realtime, a journalists' nirvana perhaps?
- Other: Sky's the limit
On the side note on the possibilities, here's a link to an article that reports the US Department of Homeland Security tagging twitter as a "potential terrorist tool":
... well, there are tons of social networking sites on the net can be used for information gathering and as communication medium for both legal and illegal activities. There's nothing new about this.
"Google Alerts are emails automatically sent to you when there are new Google results for your search terms. We currently offer alerts with results from News, Web, Blogs, Video and Groups."