Scott Miller,'s Chief Architect writes about the architecture powering Thoof, and the open source products they use. Of course Wicket is one of the products they used (otherwise there would be little point in linking to the article).

Scott writes:

[...] we wanted to create a flexible platform for the website. Not just for delivering pages, but for implementing complex functionality quickly and easily, and with performance in mind.

And regarding Wicket:

[wicket] allowed us to modularize components of the site, and gets a lot of the basic plumbing of logic and presentation out of the way.

What is interesting in my opinion is that Wicket itself is not mentioned as a part where the focus was when tweaking the architecture, but rather the database layer. Instead of using Hibernate, they opted to use iBatis instead:

Unlike typical ORM frameworks like Hibernate, or even more “hands off” systems like those employed by Rails, iBatis lets us write the SQL queries. This is more work on the front end, but gives us much greater flexibility in the long run.

Scott didn't write about the specifics of the servers they run on, but claims to reach 50 requests per second. There is no mention on memory usage or the number of sessions they have on each node.

All in all, it seems that technology is not in the way of Thoof's success. I already like a lot of the stories posted on the service. But I suspect it still needs to grow as a community (and need some way to build that).