> How come we don't see Youtube, Yahoo, Facebook suspended? Do they have procedure in place?

Yes, they do. And if you allow users to post content, you should too. You need to formally register as a hosting company and have a DMCA process published and usable.

First, register here:

http://www.copyright.gov/onlinesp/

If you've done it right, you'll get one of these:

http://www.copyright.gov/onlinesp/agents/a/auganllc.pdf

Then post a notice on a Policy page linked from every page of your site. For example:

In compliance with the Digital Millennium Copyright Act (the “DMCA”), please send DMCA notifications of claimed copyright infringements to: Advection.NET c/o Jonathan Band PLLC, 21 Dupont Circle NW, 8th Fl, Washington, DC 20036, with electronic copy by e-mail to...

Pursuant to the DMCA, Advection.NET will terminate the accounts of repeat infringers. Advection.NET will cooperate fully with any civil and/or criminal litigation arising from the violation of this policy.