>>311
I searched for info about it on the net, and found the niconico douga's press release.

Acording to that, as of March 20th 2008, subscribers of niconico douga has reached 6 million people.

If you can read Japanese, check here.
http://blog.nicovideo.jp/niconews/2008/03/001026.html

Niconico's users are limited almost to Japanese people so it's natural that users of niconico are far less than youtube users. Niconico is based on Japanese language only while youtube is based on English, which is the language whose speakers are a lot more than Japanese speakers and youyube is doing localization which means if you access youtube from Japan, the pages of youtube are shown basically in Japanese. If you access it from China, then pages are shown in Chinese.

Even if you live in US, if you change settings then pages of youtube can be seen in your preferable language, say, Italian or whatever.