Chris Bowler (he wrote this over a year ago, but it sounds like he wrote it this morning):
Twitter spent the early years building up as many users as possible — due in large part to the third party apps that accessed the service — and decided to put off figuring out how to make money off of their service until later. Now that they have the users, they seem to have no remorse about commoditizing those users and cutting out the very people that helped Twitter become what it is.
And be sure to read the concluding paragraph in Chris’ article. He hits on the same reason that I (and probably many of you) find this transition to be so frustrating.