The very cool kbalertz site now has RSS feeds. Theoretically this is cool, and yet I don't think I'll be switching from the e-mail based version. Why? Because you either subscribe to one giant feed of all KB items, or you subscribe to one feed per KB category. I certainly don't want all items, but I don't relish the idea of adding 50 new RSS feeds to my blogroll either. OK, that's an exaggeration, I think I monitor about 10 categories currently. But even that's a lot of new feeds to poll, and I could easily see that number going up over time.
So that raises a notion that I haven't really seen yet - fully personalized RSS feeds. What I really want is select the categories that I'm interested, and subscribe to one RSS feed that includes all of those categories. For individual web logs, this kind of filtering isn't as useful (although I could see filtering on post categories). However, as more companies provide RSS feeds, I think this type of customization will become increasingly useful. I'd love to see it on the MSDN Feed, for example, so I don't have to slog through posts about developing for Visual FoxPro. Trade feeds like InfoWorld, eWeek, and PCMag would also benefit greatly from this kind of personalization.
Personalization would of course complicate the back-end, and I don't know how the client would identify itself to the server (cookies? query string? authentication?). But it would be pretty sweet.