omg yes i have very organized collections. i have my favorites folder that rarely gets used (poor folder), then my Hunger Games folder, then my Nature Photography folder, then my Photography folder. then sometimes, I'll be so used to putting stuff in one folder that when i go to another topic, i put it in the wrong folder!
Nice! Yeah, I've found that I like having folders specifically for journals, too. It's a nice way to keep that information where you know you can find it, but not having it specifically displayed in your Favourites.
Do it! xD I really wish you could have a folder in a folder, though. Like my Fanart and Fanfics folder, then I could sort which fandom each deviation is from. (fanart of Ratchet and Clank, Spyro the Dragon, Regular Show, etc.)
I would if I were in charge of any groups or had a high rank in a group, but currently I'm not leading or a senior member of any groups so I can't really say weather I would find it helpful or not.
The system I mean is that when I create a collection, I can go onto that collection and create a sub-collection. For example, I have a collection in my favourites entitled "Video Games" which I would create a sub-collection for each series of Video Games, like "Spyro the Dragon" or "Mass Effect". Kind of like when you create a folder on your computer and in that folder you create another folder. It helps ones self and others browse your favourites and even ones gallery, with greater ease when attempting to locate something, in particular. Say someone makes a series of comic, I usually only favourite the first page and just use it to access the rest, as most users create links from the first page to the second and onwards. But if I could create a sub-folder I'd favourite the entire series, heck if I could create a sub-folder in the sub-folder I could make it even easier to find the chapter I last read. Applying a feature like that to groups would also, in my opinion, aid in organizing everything so everyone has a higher chance of having their work viewed.