Knowing just a little of marketing business it basically an equation of supply and demand, when demand would be the amazing popularity notpron got, therefore I think you should give it a try first. don't underestimate adding profitability as it might surprise you.
I wouldn't mind having a banner or a middle screen on each level, but I think pop-up is a very bad idea since most browsers today blocks it.
As for a minus levels account, I would think again since some of us are using more then one computer and different IPs from time to time, and it may cause some problems. although it's a sure income at first, that's where it ends - at the... lets say... 50 of us who will pay for it a fee of... just throwing a number... 5$ to 20$ (as been suggested here) it would get in the best scenario to a 1000$ but that would be it, when adding would fly by it in no-time. in the world we live in today there are commercials practically everywhere, if it'll help keeping notpron and all that comes along with it alive then why not here?
About the google bar, if I'm not mistaking it, it's 3 cent-a-click, and if David really wants he can build up a page the automatically refreshes as fast as the computer can stand.
As I said earlier, I'm willing to go with the flow here and accept every decision whatever it'll be, but I think you should give a thought for those who want to help but can't finance it. I'm sorry, but if we are a community as been mentioned here more than once, we should take care of everyone, and not only for ourselves.
P.S. Wow David, I think that at the end we'll make you a very rich man!
