I hear a lot of OOP fans say that OOP makes large applications "easier to maintain", and the question always comes to mind "Easier for whom?". If I ask "Who will be maintaining my application?", the answer is "ColdFusion developers", and if I ask "Which programming paradigm are ColdFusion developers generally more comfortable with?", I would have to say the answer is "Procedural". Here in the Orange County/Los Angeles area, it's hard enough to find a decent CF developer without limiting my search to the small amount of people that claim to be OO programmers (and some of those aren't even really OO programmers, they just need a job and will say anything). Not to mention that the CF Developers that really do know OOP are often more expensive than their procedural counterparts.
I am not an OOP guru, so my opinion may not be firmly planted in reality, but I don't think the size of the application really matters when it comes to deciding weather to develop it in pure OO code or to develop it using procedural code and maybe sprinkling in some OO concepts where it makes sense.