ExecTweets is a site built by Federated Media and endorsed by Twitter.  It offers a simple value proposition: find influencers by topic, view their conversation and engage with them, all within a single evironment. 

While this looks like an afterthought, ExecTweets' Twitter 101 page is fairly well written (though clearly not part of the core value prop, at least at present).

Twitter has long needed a directory of their leading personalities.  And advertisers have long sought out a solution to capture the momentum of the Twitter phenonmina. 

Advertisers pay for three things: position/placement (attention), relevance, and engagement.

ExecTweets offers tangential access to the Twitter audience.  It suppliments the twitter user journey.  It builds on Fed Media's value proposition.  But it does not solve for Twitter overall. It does not integrate with the Twitter experience, with 99% of the twitter activity.

 ExecTweet advertising is equivalent to advertising in an interactive yellow pages.  Yellow pages do not define the phone experience, they suppliment it.   I strongly doubt that there is enough interest in advertising in a suppliment, to support the core Twitter experience.

Federated Media has established their value as a business and within the social community by bringing all these three advertising attributes (attention, relevance, engagement) to brands in a deeply social manner.  They accomplish this by bringing compelling social personalities and their social audiences (blogs, twitter etc) to brands in nicely packaged formats, such as sponsored blogging from an influencer on a brand site.

Advertisers few alternatives for reaching the Twitter audience.  Fed Media has credibility all around.  Twitter is gaining a valueable resource.  Everyone wins.

Alltop.com is ExecTweets for blogging.  Alltop aggregates all of the leading social voices by topic and features their latest posts.  While Alltop is a great resource, it has not changed the way we publish, interact with or engage with blogs.  It hasn't changed the blogging experience, it has supplimented the blog discovery process.

The same is true of ExecTweets.  It's a great resource.  But it isn't part of the Twitter experience.