Car sharing: leading to increase car usage ?

I just want to raise the discussion on I believe was the main goal of the majority of the car sharing companies: to reduce overall environmental impact of car usage. The main argument about the positive environment impact can be summarized in two main points: (1) less occupied space (each car share in average represents 5/6 cars that are no longer needed); (2) less pollution since car sharers tend to use more public transport than the average automobile owner.
After doing some research I found that basically car-sharing companies in Europe are flourishing in all countries in very different formats and with very different objectives: from non-profit firms to for-profit firms, with missions ranging from green companies to “a better luxurious alternative to public transports”. My main hypothesis is that the ripple effects of car sharing will indeed induce to overall more car usage not off-setted by the increased usage of public transport. The proliferation of car-sharing companies and associations and the increase competition for clients to sustain the even-more expensive networks of cars and locations will probably lead to a competition on prices hence resulting in the democratization of car-usage. Even more, the increase in size of these companies will lead to the weakening of the their neighbourhood/ communal feel and associated auto censorship of excessive car usage.

Another factor that in my perspective will also lead to increase usage of cars are the creation of international car-sharing networks like European Car Sharing that, among other benefits, enable international mobility of members giving them access to local car sharing networks. Basically when abroad people will now have access to a cheap and accessible fleet of cars hence not needing anymore to recur to public transport (one of the main means of transport when abroad).
Although with no scientific sound facts to back out this hypothesis I do think that one has to step-back and reflect on the possible ripple effects of such a huge boom in the car sharing industry in Europe and in the US (e.g., City Car Share - http://www.citycarshare.org/) Will it attain its main objective ? Are alternative/concurrent business models more valid, as lift sharing ? (http://www.liftshare.org/)