It depends upon the business logic of your application in some cases session may be the best choice , however there are lot of alternatives ,Session should be used if you are having different data for each request to your application ,you can post your data in hidden fields with your forms , but again ur question is a little bit of the track, You have to analyze your requirement than according to it you have to decide whether to use sessions or some other alternate solution , If I have to store id's of users than definitely I will go for sessions cause it will be different for each users , I would not keep very big data in session like keeping a dataset in session which few developers do . Then also questions comes if ur using session where u want to keep it in process or in server , if ur saving session in server it is very costly but in ssome scenarios its very useful .
