Google put the Ajax development method on the map with the launch of its Google Mail service, and now there are more than 50 websites taking a similar approach to online applications.
These sites, such as Backpack, Writeboard, Writely and Zimbra, are at the forefront of the hype surrounding Web 2.0, a new, more collaborative internet.
First, the bulk of the code is running locally on the user's PC, which makes the application richer and more responsive.
Second, the application runs without constantly going back to the server for page refreshes, and this minimises network traffic.
The advantages include the ability to access an application from almost any PC anywhere, such as a cybercafe, plus zero installation and maintenance.
Nonetheless, Ajaxing delivers many of the advantages of the application service provider model without the dire user experience that is common with web-hosted applications.
There are also disadvantages. Web-based applications are generally slower and less powerful than ones that run from a local PC hard drive. They are also subject to network problems and other downtime.
And perhaps most significantly for a corporation, they involve storing important data with a third party, which is often an unknown entity. Ordinary users are unlikely to keep local back-ups of their web-based data, even if they can figure out how to do it.
Also, there is generally no guarantee that the third parties entrusted with all this data will either keep back-ups or meet acceptable standards for data protection and privacy.
Web mail that uses Ajaxing is better than just using HTML, as is clear from comparing "standard" Google Mail with the fall-back HTML version - but it does not help if you are trying to prevent staff from using personal mailboxes for company mail.
Indeed, Ajax applications may be even more dangerous, because the trend is to allow data sharing and collaboration. For example, there is no real benefit for an individual in using an online program like Writely - you might as well use Wordpad. The advantage is that you can easily share the Writely text with someone else, or everybody else.
Still, Ajax is going to be big, because it makes it possible to give any web-based application a rich user interface. This was why the first Ajaxing application - Microsoft's Outlook Web Access - was developed, and why Microsoft is now planning more.
Some of these new Web 2.0 applications will be aimed at enterprises, and some will allow companies to run them in-house on their intranets. Zimbra, a rival to Microsoft Outlook, is an example.
Google has established Ajaxing with Google Mail and Google Maps. Now everyone has to do it in order to compete.