I stopped to write reviews for MathSciNet because I think such information should be completely free.

You are a kindred spirit : so did I. I no longer write for Zentralblatt either. Why should I review papers which are not freely available to me, or to almost everyone ?

It did occur to me to review papers from the arXiv that I like, but there is no place really where these reviews could appear. If someone starts a substitute for MathSciNet or the Zentralblatt, I would be willing to contribute in my small way.