[Zope] Social Networking over Zope

[Pablo Ziliani]

Hi all,
I have recently been asked to build a social network site. My first 
thought was to implement it on Zope, but I'm a little bit worried about 
concurrency and scalability. Having such a site access continuously to 
the database, I guess its caching possibilities are very low.
Anyway, what I really looking for is some advice. Anybody here to share 
his/her thoughts? Any past experience? Why is that most social networks 
are built over ASP.NET or PHP?

Thanks in advance, a lot.
Pablo

PS: I still have to convince my client, so...