session vs request

[Jesse Vitrone]

I have always learned, don't put stuff in the session unless you have 
to, so when I started my project, I made all of my backing beans request 
scoped, but started wondering lately if there are benefits to keeping 
them in the session.

Is there a valid argument for making them session beans?  You could 
argue that you're using less database resources by not having to hit the 
database over and over for the same information that you've already 
gotten.  Less network traffic because you're not passing as many request 
params around all the time.  Less code in your jsp's because you don't 
have to write out hidden fields all over the place.

Are these points enough to offset the server overhead of keeping this 
info all the time in the session?  I guess it depends on how many 
concurrent users you have to worry about.  Is there a rule of thumb for 
how many users you have before you start to kill your server with too 
much in the session?  The project this is for is a pay site that you 
have to log in for, so it's not going to have the thousands of public 
users surfing the site at one time, it's more like a thousand users 
total and *maybe* a few hundred logged in at a time.  Is that enough to 
worry about session sizes?

Any other arguments for or against sessions over requests?  Am I crazy 
for even considering making most of my beans session scoped?

Jesse