I wanted to give my 2 cents, so here goes;
For me it's a combination of factors.
Firstly I'm 10 years older than when I first started heavily collecting, my situation and priorities in life have changed. It's crazy but going from being single and living with parents to married and owning a house does things to your outlook on life (and mainly your wallet).
Secondly, as others have mentioned Oakley is a different company to what it once was. I'll never forget the feeling when my Dad bought me my first pair of Eye Jackets (Gold X/Gold EJ's if you were wondering) as a present (he bought a pair but in Corten), I really did feel that they'd come straight from the hands of a mad scientist, via a little eyewear shop, to my face. Oakley was small, independent, adventurous and making, as far as I was concerned, the coolest damn things you could put on your face.
I chased that memory of my first pair for many years, I won't trivialise substance addictions by saying that it was like a drug but I wanted that same feeling, I wanted the excitement, the buzz of getting that first pair in the early ninteies. Of course I also tried to find the older pairs that I couldn't afford at the time, to buy new release pairs where the detailing made them like tiny works of art (the sculpting and detailing around the orbital and frame of a pair of Hatchets still impresses me today)
Put simply, Oakley seemed to me to be a company that would stop at nothing in the pursuit of making the highest quality, best engineered and stylish glasses. No made in China to the lowest bidder, no strange mishmash of styling lines throughout a frame, no distorting/eyeball ruining cheapo lenses. It was something to which there was no comparison.
Sadly I just don't feel that today. The company is huge, yes the lens technology is still there (and switchlock is neat) but the passion, the little details, the things that I felt made the difference just don't seem to be there anymore. A big model line with a number of (in my opinion) box-ticking pairs, it feels like another huge company trying to hold on to its (Mad Science) roots whilst at the same time being forced to meet the demands of a remote, purely financially driven, corporate office.
All that said, I still find myself doing a double-take if I see someone wearing an unusual/uncommon pair in the street or catching a glimpse of the Icon being used in a film or TV ad and I don't think that will ever go away. Ever since getting that first pair of eye jackets I have never purchased any other brand of sunglasses (to date) but these days there is no buying a pair just because it's a new Oakley release.
Over the last few years I've chipped away at my glasses collection from 80 or so pairs down to about 50, the ones that remain are things I can't bear to part with (those first EJ's or my 0.2p for example) or things that aren't worth a jot (banged up e-wires) and I'm sure that over time some will come and some will go but at a leisurely rate and without sitting on ebay for 8 straight hours, through the night just to catch things being listed in the US...
When it's all said and done, I had fun and I met some great people along the way and I wouldn't change it for a thing.