Dr. Falco Maltese
There's more, like if you need money to pay shady or to buy equipment, you can borrow it, or you can ask agency members who are "in" with a faction to buy something for you that their faction sells.
Also members can leave cases in the files that they don't have time to solve, so you might end up with more than your eight cases per day.
I have found the most fun thing is getting to know a group of great people. I miss them when I am on by myself; the game is not as much fun when I am not chatting with the others in my agency about what we are doing!
In sum, if I had never subscribed and joined an agency, I'm not sure I would still be playing. To me, it is very worth it.
Hope that helps!