Often we will do something just because we have the technical ability to do it. When performing a live search (ajax-enabled searching), it is just as easy technically to get the results on each keystroke.
Dunston Orchard of Apple has a nice approach to LiveSearch that he presented. Check it out at 1976design.com/blog. (I suggest searching for 'puppy')
Here is the user experience issue. When the user types in an Ajax-enabled field do they want the search to happen at every keystroke? This is the approach Bitflux took. Like Dunston, I find this sort of approach annoying. Dunston provides several nice touches to his live search feature.
- as soon as typing stops (appears to be half second) the search initiates.
- you know it initiated because you get the apple style spinning wait circle
- the list fills in
- details show in very cool callouts as you hover over the summary results.
However, I experience about a half-second confusion as you wait for the search to initiate.
Maybe allowing the Enter or Tab to initiate the search instantly and would alleviate the confusion (at least for the keyboarders).
BTW, while you are his site read about the panarama banner at the top. Marvel at his slide downs-- way cool and check out the balloon details that show as you mouse over the live search results.
Anyway, the moral of the story is: Remember the user is more important than technical prowess. Just because you can do it, does not mean you should do it.