best way to host a membership site

[Magdoll]

Hi,
      I know this is potentially off-topic, but because python is the
language I'm most comfortable with and I've previously had experiences
with plone, I'd as much advice as possible on this.

I want to host a site where people can register to become a user. They
should be able to maintain their own "showroom", where they can show
blog entries (maybe just by linking to their own blogs on some other
blog/album-hosting site like Xanga), put up pictures (again, I'm not
thinking about actually hosting these data, since there are already
plenty of places to put your pictures and blogs). The most important
thing is they will be able to build up a "profile" where I can store
in a DB. The profile will include membership information - for now,
think of it as "member X owns item A,B,C and gave comments on A such
and such, also member X is a male white caucasian between his 20-30
who likes outdoors". Eventually, I want this to be a simple social-
networking site where people can share a very particular hobby (I'm
doing it for comsetics and for a very targeted group that are active
bloggers, so they'll be somewhat web-salient) and the backend can
collect enough data (while maintaining privacy) to build up a
recommendation system similar to Netflix's movie recommendations, or
Match.com if you will.

I want to know that given I know python best and I abhor C#/ASP, what
is the best thing to use. A friend recommended Ruby on Rails - not to
instigate war here, but I'd welcome comments on that (I don't know
Ruby, but I'll learn). I've used PLONE before, but back then I
remembered the site ran incredably slow (or it could just be the
server), and there were issues with upgrades. I want to minimze time
on trying to learn how to write an interface for users to register and
manage their own space. Also I want an infrastructure that's not too
rigid so if in the future I want to add more apps it's not to hard.

I've also heard about django, but not enough to know how far it'll get
me. I'm open to all sorts of suggestions. Thanks!

- Magdoll