What would you think if Twitter charged users to access their service?

What would you think if Twitter charged users to access their service? In terms of customer's paying to use Twitter, what do you think of the "buy up" concept. That works well with game programs. The first 15-20 levels are free... you pay for the next 50. Those that really enjoy the game will frequently buy in to the full version. Is this something that Twitter could do? The first 100 tweets are free then you have to have a paid membership to do more?Class... how would you feel if Google implemented this concept? Let's say the first 250 search are free each month then you pay 1 cent per search