This is the perfect time to start charging users a monthly fee [for Twitter]. Why? Ad-supported sites cannot survive in the next 12 to 18 months, perhaps even longer with our current economic
environment. If you start charging, others in the social networking space will follow.
In the next year or so the argument that if you charge users go elsewhere will be bogus as only those that
generate revenue will survive. Those without revenue, i.e., the social networking business ad models, will slowly die.