Sponsored Tweets at least announced that the content was advertising. I think this language will just lead to advertising without proper disclosure by the user (which was used in keeping with the FTC ruling on this issue). Some celebs & bloggers will still accept money & Tweet about products, just without indicating publicly that they've been paid.
Also, you say "We don't seek to control what users Tweet" but that's exactly what you are doing by preventing users from Tweeting advertisement should they wish to. I know you can set whatever rules you like regardless of how they affect people or developers but don't make a ban on using Tweets for certain kinds of content and then say that you're not trying to control the content. Clearly, that is what you're doing. That's what a ban is, exerting your control over content. In my opinion, you've picked the wrong target. I'm also not sure how "paid Tweets" by individual users is any different from commercial/organization accounts using Twitter to offer discounts, specials, sales, etc. Why does the advertising ban apply to individuals and not to companies? Liz Pullen