Are you suggesting that going back to the db each time is more scalable, or that I am better off using some kind of method level cache?
Honestly - just wondering - any good articles on what you are discussing? I guess I just don't quite 'get' it - not having worked on an application that scaled to the point that session access was the bottleneck.
Yes and yes.
This is a really long and deep topic. There are all sorts of reasons why sessions are not a good idea. But let's stick to scalability.
If you're using your session as a sort of cache for objects, that's probably okay (although, consider using something designed for this, like memcached). The point is, you ought to be able to reconstruct all the objects you need from just the request parameters.
This is a pretty good article about it all.
"Session State is Evil" -- http://davidvancouvering.blogspot.com/2007/09/session-state-...
I'd like to emphasize this point in particular. Shared state is a big, inefficient, centralized bureaucrat and is the enemy of horizontal scaling. Statelessness and decentralization are best-friends-forever (they each have a denormalized copy of different aspects of the same friendship bracelet!), and you should figure out as many ways as possible to exploit statelessness and minimize unnecessary shared state in your application.
If you have the time, learn statelessness-in-the-small as well: play with a strict functional programming language (for your own edification, not necessarily for implementing this particular project!), and you will learn how to become keenly aware of the flow of state in any program, and how to maximize statelessness in any language. This will improve anything you ever program again, and will form a powerful mental model of state that will carry over by analogy to statelessness-in-the-large.