I see what you are saying. It just seems like an akismet-style filter to catch known spam and such would be a natural next step, so that even feeds on a given service that were not highly tended by their owners would not become swarmed with spammers.
This is an interesting idea. Tagging meets meta-tagging meets microformats. Why limit it to microbloggers, either? It seems that any of the social services would benefit from such a rich form of tagging. example:
Last.fm
for bands %%0 currentmembers="" %%0 pastmembers="" %%0 awards="" for songs %%0 covered=""
Great post, Robert. I have to say that, increasingly, it seems that anything that speaks of reason, ethics, or even basic fairness (the fairness of kindergarten, not Mill's "On Liberty") is "unAmerican".
good post! {seesmic_video:{"url_thumbnail":{"value":"http://t.seesmic.com/thumbnail/D4s42XRG8W_th1.jpg"}"title":{"value":"good post! "}"videoUri":{"value":"http://www.seesmic.com/video/XlBczsHyEg"}}}