Can WP MU handle 50000+ users at one go?

Hello all,

I have just started learning WP MU. I think its wonderful. I have worked with WP before and I loved it. I hope WP MU provides a great working experience too.

I am developing a site using WP MU. I wanted to know if WP MU can handle loads of up to 50000+ users. We also plan on using plugins extensively. Would that affect the site's performance in any way?

Also needed to know, whether Buddypress is an extension of WP MU or its just something that is completely different? Since I am developing an interactive site, would I need this API as well? Does it integrate easily with WP MU?

Lots of questions there, but I have been reading the forums, people seem really helpful !!

Thanks in advance,
Sib