Twitter has reportedly been valued by investors at $1 billion. Oprah's on board. And the company's founders are set to headline the high-profile D conference tonight. So it's odd they seem to see their own product as a repository for jokes about cleavage, bird shit and killing Jason Calacanis.

Twitter allows its users to mark some tweets they find particularly amusing, insightful, witty, informative, or whatever as "favorites." Rifling through the founders' favorites is a pretty good way to get a sense of what they think Twitter is good for: crude jokes and narcissistic status updates. The below tweets are culled from the Favorites lists of co-founders Evan Williams, Biz Stone and Jack Dorsey. Dorsey is the one who faved the frat-boy-ish Calacanis item.

Ideally, from a business standpoint, Twitter executives would be highlighting innovative uses of the service — from hard news to customer support to more creative forms of tweeting — if only to help spread it to more users.

As Stone told the Wall Street Journal today, "we need to make Twitter the product more relevant to more people." Hopefully they'll highlight some ways to do that tonight at D. Because the founders are not always the best at doing so with their own tools.