PG, sorry, but I am a little confused by your answer.
Is your "yes" in response to "do you still feel comfortable with the suggestion to build companies on top of it?" Or, to the fact that you would now recommend other companies and startups be "cautious about building anything on Twitter after" the new Twitter TOS and other policy changes there?
Are you removing http://ycombinator.com/rfs3.html from the Y-C suggestions?
My team and I were hacking on our site to launch http://tweeplayer.com at SXSW exactly at the moment the new TOS came out, and it freaked us out at the time. But, the gist I got from people in the know was that as long as you are helping Twitter get content they wouldn't get on their own, they will likely be happy with you.