I searched through Google as well but I could not find the answer, so please help.

Question-1. How many social bookmarking sites are there on the WORLD WIDE WEB ?

Question - 2. How to find these social bookmarking sites ? Please don't tell me to go to vmoptions or web-directory.ws or socialmaximizer I have already finished these sites. Seriously I want to know that how can I find all the social bookmarking sites which are available on the WORLD WIDE WEB ?