They might be your tweets, but the money is all Twitter's: The microblogging service must now get a cut of any advertising sold against Twitter content, even your own content. Nice racket.

Here's how the Twitter business now works: Millions of people, including elected officials, Hollywood celebrities, you name it, supply the San Francisco startup with a huge quantity of free content. Twitter publishes this content, gets the right to sell ads against it and—here's the new part—gets a cut of any ads sold against the content when republished elsewhere, according to new terms of service noted by Peter Kafka of All Things D:

In cases where Twitter content is the basis (in whole or in part) of the advertising sale, we require you to compensate us (recoupable against any fees payable to Twitter for data licensing).

This means, for example, that the Huffington Post must give Twitter a cut of any money it makes selling ads against one of its Twitter editions, which syndicate tweets from a wide array of writers. HuffPo would get paid, Twitter would get paid, and the writers who created the actual tweet content would make nothing.

So let's say one of Twitter's more popular writers decides to republish his tweets to his own website, so that he might sell some ads and profit off his own work. Well, it looks like Twitter is entitled to a cut of that money too. Under the Twitter terms of service, "you have to use the Twitter API if you want to reproduce" tweets, and using the API subjects you to the previously-quoted requirement to cut Twitter in on any ad money, a requirement that would seem to override Twitter's vague statement that "you retain your rights to any Content you submit."

Twitter also must be cut in if someone goes around to, say, 15 different tweeters and makes a deal with them to syndicate their content.

And what's scary is that it's Twitter that gets to decide how much of a cut is fair. Since the accounts live on its servers, Twitter hold all the cards. So there's not going to be any negotiating. They might be your tweets nominally, but any money you make belongs to Twitter. You keep some of it entirely at the company's discretion.

Now get out there and make Twitter some more money. The journey to $1 billion market cap starts with just 140 characters.

[Pic: Twitter CEO Ev Williams, Getty Images.]