redirect_to(session[:return_to]) vs session.delete

If you are on Rails 3 use redirect_to(:back)... if you are not then
the only real implication is having trash hanging around in your
cookie storage (if you use cookie storage.) for db storage it's meh on
the space used because it's most of the time trivial but it still
leaves a dirty session. So at the end of the day it depends on how
thorough of a programmer you want to be.