I prefer to comment on another person's weblog instead of commenting on my own because (a) it keeps the conversation in one place and (b) the author is almost sure to read the comment if I post it there. As a consumer of weblogs, I find the comment saying "I've blogged a response: <url>" to be extremely annoying. The lack of effective (spam-proof) trackback functionality is another reason I avoid doing that.
Right now I'd rather not have my comments aggregated at all, anywhere. But, if I change my mind, I want to be in control of the aggregation--who does it, what content is aggregated, what details are disclosed, and how much I am compensated for it.
I think eventually all search engines will have to do revenue sharing with content producers. Because, while search engines provide a useful service (even Backtype might be useful if it had a bigger index), they cannot exist without content to index. Plus, search engines are increasingly competing with content publishers (e.g. Google Knol, everything on Yahoo).
So, really what I am opposed to here is the opt-out (instead of opt-in) nature of the republication. I would be less opposed to it if there was an effective and convenient way to opt out of it. It seems right now the only ways to opt out are to file DMCA complaints and/or lobby websites to exclude the spam bloggers' robots in robots.txt.