Adaptible systems

For all the user-adaptable systems out there - a perfect system would need to make "errors".
That is, the perfect system would not only adapt to what the user thinks they want.
The best algorithims in evolutionary (? Adaptive?) programming allow for unexpected mutations and fluctuations. What is then the best balance between adaptability to existing data and the capacity to crunch completely novel input?
How much can we as users take in and process? And how much of this can be transfered into a simple (or even complex ;) algorithm?

--------------------

One thing that bothers me about XML and RDFs, podcasts and rss feeds - they are flat, the dimension of time is sorted by autoupdates. Any other options (formats/languages) competing here? Is there any future in (and now I KNOW I am confundling concepts) multi-tiered AJAX?