So apparently, Twitter is hiring a product manager, to focus on revenue generation. Hopefully an all star development team to stabilize the platform and kill any remaining bugs is on the list of to hires, but I digress.
For Twitter, or anyone applying for the position, may I suggest... suggestion?
Twitter, you already ask people what their interests are, and even on non-technical interests, have sizable audiences. The tweets don't always follow one niche or topic, but you know what topics are trending and where interests lie.
To blatantly steal a page from e-commerce merchants, why not offer suggestions? 85% of the sites I visit (and this is a completely unscientific figure) take a look at the products I view and offer suggestions based on browsing, and in certain cases my purchase history.
If you can segment tweets and followers by niche, surely there are commercial sites who would pay to have their conversations suggested. For users, it's less intrusive than a keyword ad, less out of place. For advertisers, it offers a chance at an audience that lasts longer than a click or view. For you, Twitter, it encourages higher quality tweets. Advertisers not posting anything of interest will have to make their tweets more interesting or relevant, or no one will follow.
Just a suggestion