Please don't kill me for this, if it's bad, don't start a flame war or anything, just make a polite comment and leave it at that.
OK, here goes. I think there should be an interest system set up to encourage people to make money and save it (just like in real life). However, there need to be some restrictions put up on the interest system. I have no idea how much interest you should get, that's not for me to decide, certainly something like .005% a day or lower though because otherwise there would be a huge jump in the economy.
Also, it should not be automatic interest, then people could leave the site for a while because they got bored, come back, and suddenly have 2 mil when they left with 200k or something, definitely not so great for the economy. There should be a "collect interest" button or something that players have to press themselves once a day in order to get their interest.
Sorry if this has already been suggested and I didn't notice, but it wasn't in the first 7 pages of the board and I didn't really want to scan the rest of them, so I figured it was safe to suggest. Again, suggestions on improvement of this idea are welcome, as are criticisms and (most of all) support, since as of this moment the bank serves no purpose beyond putting your tu in so you don't spend it all on a whim, not really all that useful.