This is not good news. Many, myself included, use third party clients exclusively. The Twitter website and official apps just aren't what I'm looking for. The official clients have different priorities, including advertising and expanded tweets. I'm all for Twitter making money, but I'd love to be able to continue to use my client of choice.
The Next Web has a good post that tries to pull together some of the sentiment of current third party developers. It will be interesting to see how this develops over the coming months.