I agree. For example, why do we look at email ranked chronologically? I'd much rather rank it by relevance or importance (or my likelihood to actually answer it).

The feature set includes sender, recipients, whether I'm the only recipient, time of day, words in the subject, words in the body, and whether I've exchanged messages with the sender recently.

There are still another few days left to apply to YC...

I wouldn't be surprised if GMail gets a feature like this at some point. Google Reader already has an option to rank RSS feeds by what it thinks you're most likely to read, so similar technology already exists at that company. The main (massive) issue would be teaching the filter.

Do the scripts have the ability to change the weight of features on the fly? For example, sender becomes the most important feature when the sender is, for example, my boss or particular end users. Otherwise, other features may be more dominant.