I see. I suppose smaller (especially browser or mobile) games would need more progressive advertising, and if devs are busy pumping out a game each month or so then such deals are very convenient. The idea of selling the whole thing for a single payment is just very odd to me, but I'm not familiar with developing small browser/mobile games so eh, sorry for speaking too soon I guess ^^;
No revenue share is kinda scary though, ya never know just how successful your game could end up.