Andrew, after reading that Jason found yet another person republishing Weblogs, Inc. content, asks the question again: Do RSS feeds give an implied license to republish?
You probably already know what my answer will be. (Hint: the content's medium alone does not eliminate the author's rights in that content). Karl-Friedrich Lenz also answered the question recently:
Decisions about licenses are not based on what users "assume", but what copyright holders want. If I want to give everyone a license to mirror my blog except Google, because I think they are in the spyware business now, that is the license. If I decide I don't want to give any license at all to anybody, all "assumptions" of users will be just wrong.
Perhaps, however, syndication advertising is the answer to this problem.
The appeal of syndication is that it makes it very easy to repurpose content. This is true for those with good intentions (ie personal use in an aggregator) as much as it is for those with less noble intentions who want to benefit from your content.
When the feed has advertising in it, such a republisher has two major options: 1) do some extra work to strip out or otherwise modify the ads or 2) republish the full content, including the ads. Sure, it's a relatively trivial task for most coders, but it's still an additional hurdle that must be overcome. Besides serving as disincentive, it's also a good way to tell what someone's true intentions are with the republication. If they went through the trouble to strip it, it's pretty clear they're not innocently republishing.
On the other hand, if they republish the full feed including the ads, the creator is compensated for the misappropriation. In fact, the republication may actually be welcome, because the wider audience will enhance the total value of the content.