I believe it is the author's responsibility to restrict what he puts in his RSS feed. Sure, there are automated methods of extracting CC licenses (see http://creativecommons.org/technology/usingmarkup). But it's the same as with all content on the web: Lead Me Not Into Temptation. You can't very well publish everthing in a convenient format that is MEANT for syndication and then complain when people do it.

On the other hand, it's equally clear that feed aggregators shouldn't piss off the content providers. On my humble http://www.blog.ch/ I only publish the title of each blog entry, complete with THREE links per posting going back to the original site: XML feed, homepage, entry's permalink. I believe this is beneficial for everyone involved: Visitors can see what's going on at a glance, and content authors get qualified visits.

The only downside: People immediately subscribe to the feeds and never come back to my site :-(.

Matthias, you can do what is called feed-splicing – that is, aggregate RSS feeds to create your own RSS feed. The simple service is it might save people time subscribing to several feeds at once – however the moral and legal sides are up to explore... some people wouldn't like it, I'm sure.

Oh, they can subscribe to all feeds at once, I've got an OPML file – although, as usual, not all tools can handle it. Either the OPML specification is too loose, or the tools are too unflexible.

I've been considering feed splicing for a couple months now. I'll probably do a trial and see whether people are OK with it or not.