Twitter's all about self-promotion. This we know. MC Hammer knows that, too, and apparently has been quite successful at it, which explains why Gravity Summit invited him to keynote this week's social media conference at Harvard.

For those of you who don't know, Gravity Summit describes itself as a "bridge" between social networking media and business leaders. Basically, it smacks business leaders upside the head and tells them to use Facebook, Twitter and all those other sites to help make money. We're not sure what kind of money MC Hammer makes these days, but he has amassed more than 1.3 million followers on Twitter.

Perhaps it's because of his reality show, perhaps it's because of his camp value — regardless, people are getting regular updates about his happenings. And he knows what that means: there has to be a way "to sell those people something." Indeed.

That's why we've compiled a list of seven famous people from all walks who would be well-advised to get their tweets in gear to sell something, reclaim their formerly glorious profile or simply satisfy our selfish desires.

Seven Celebrities Who Should Get on Twitter Right Now

First up, Pete Rose. The former coach of the Cincinnati Reds was banned from baseball for betting on his own team. Pretty shitty. And against the rules. There were rumors recently that the ban, which prevents him from Hall of Fame entry, would be lifted, but those rumors were put to rest by baseball commissioner Bud Selig. If Rose were to get himself online and sell himself to the masses — maybe, just maybe he can get back into America's good graces.

Seven Celebrities Who Should Get on Twitter Right Now

Remember Michael Alig? Alig, the club kid who became infamous for killing his drug dealer and hacking him into tiny little bits, used to know about all the trends. (And, more importantly, be known all over town.) If he could somehow convince prison officials to grant him internet access, Alig could get a tidy online following ahead of his scheduled March 2010 release.

Seven Celebrities Who Should Get on Twitter Right Now

Oh, Burt Reynolds. He was hot, then not, then hot again and now, well, he's appearing in Not Another Not Another Movie. Sad. Now, Burt actually has a twitter page, but it hasn't been updated since November 25, 2008. For shame! One of the keys to Twitter is regularity. Considering the inactivity in your career, we're sure you have time. Go forth and tweet!

Seven Celebrities Who Should Get on Twitter Right Now

Okay, let us explain: most of the people on this list are infamous for one reason or another. Jo Beth Williams, the star of Poltergeist I, its sequel, The Big Chill and many other wonderful movies, is not necessarily infamous. Nor is she as famous as she should be: the most recent thing in which we saw her was an E! special on horrific Hollywood murders, on which she discussed poor Dominique Dunne (Dominick's daughter, who was strangled by an estranged boyfriend). Yes, there are other projects, but there should be more!

Rather than focusing on regularity, she should instead use Twitter to spread her political and/or cultural views. We suggest she start with a memory from her former soap, the soon-to-be-late Guiding Light. Time it with the news, Williams, grab a small headline or two, and then start letting your tweet flag fly.

Seven Celebrities Who Should Get on Twitter Right Now

Joan Collins remains a household name, yes, but so does Burt Reynolds. We guarantee that if Ms. Collins were to start tweeting about her private life, which we assume remains quite titillating, she would be all over the gossip rags, where she belongs. Plus, we're sure this woman can think of something to hock.

Seven Celebrities Who Should Get on Twitter Right Now

Former New York Governor Eliot Spitzer pops up every once in a while to offer some thoughts on the current economic situation, but we know he loves the limelight. And Spitzer, who hired whores, as you know, would do well to get on Twitter and start offering pithy political opinions. If you do that, Spitzer, you'll be back on top in no time. Just stay away from Collins. She'll eat you alive.

Seven Celebrities Who Should Get on Twitter Right Now

Finally, Paul Reubens. The former "Pee Wee" has been working relatively steadily since getting out of prison and, in fact, has another Pee Wee movie set for a 2011 release. Regardless, "twitter" could be the magic word for him to claim a new fan base and ensure the world never forgets. Or, at least, remembers until the next person spouts out their 140 character musings.