I don't think there is any 'greed' involved; designing and supporting a website this large requires a substantial monetary investment, even if all the mods are volunteer. Judging by the amount of ads on RR.net, I doubt that the admins are getting rich, although I have no knowledge of the inner workings here.
After investing several hundreds of dollars to build my small site (click 'my best' below), I decided to place ads via an agreement with Google. The ads generate very little revenue per month so far, although the number of visitors to my site pales in comparison to the volume here. At the current rate, the ads will never pay for the initial investment, but will probably pay for internet related expenses (domain name renewals, yearly hosting/bandwidth fees, etc); this is acceptable to me, as I do not view my site as a business, but rather a vehicle to display my photographs and share my experiences for people to enjoy.
And don't forget, not all railfan sites are free; Trainorders.com requires a small yearly fee to fully participate, and RailPictures.net strongly encourages yearly membership to fully utilize their site.
It's funny, though, with IE9 I have never experienced a pop-up from RR.net at home, but they do occasionally show up on my Droid X! Go figure....
Anywho, let us enjoy the 'free' RR.net, and hopefully the admins can work on the pop-up situation to everyones satisfaction.
Chris
"Old railfans never die, they just lose track......"
My collection My best
Supporting member: BRRHT, NYS&WT&HS, CRHS