This would have to be implemented in a very sophisticated way. For a start Coke is a business, but then so is a start-up with three employees - are you telling me they should pay the same?
It must be the case that Twitter will offer bells and whistles to big companies and charge for them - otherwise entrepreneurs simply won't use it to build their businesses.
Also you have to think about a company's revenue streams. A car manufacturer, which could conceivably make a sale from a click-through, stands to benefit a lot more than a publisher that gets money through ad revenue.
I can think of about a million other problems too.