What is AJAX? Its a buzzword? Its a fad? Yes and No. Its cool if you know what it is, its a fad if you don’t know what it is. Possibly there’s not a single web-designer or developer on internet who’s never heard of AJAX, & thats just about it. A lot of them have heard about it quite a lot & quite often but just a few know what it really is. Though the number of people aware of the meaning of AJAX is quite less, the number of people buzzing with the word, as if they are the know-it-alls on the subject of AJAX, is quite quite high.
The selling point is remote-scripting, using XMLHttp object for communicating with the server in real-time and passing/getting the data without refreshing the page. Now just because its possible everywhere doesn’t mean that its ideal everywhere.
Google is a trend setter. What they do is copied & followed up by others, be it AdSense or Blogger or massive storage in GMail or the enhanced UI in GMail. I for one believe in setting trends for others to follow rather than in following in someone else’s footsteps. I’m not a sheep in the herd.