I also pretty much have all my music in M:\ (Music) . I do have a few subfolders currently, as I'm still trying to find the time to do some serious cleaning, but eventually I'll have all Music in that folder, with perhaps an Import folder.
I put the basics in the filename, store the tags in the files and MC backups the library so often that I don't worry too much about it. I don't have to scan subfolders in windows explorer, it works for me. This is usually sorted by default in most programs in a useful (to me) way...
[Artist] - [Album] - [Track #] - [Name] - [Genre]
It lets me forever restore the most important tags except in perhaps the worst of disasters. I'm not saying this is the best way, but as was originally stated...
There is no right way but we can develop a set of options for new users.
Once you get used to using the database mindset with viewschemes, smartlists, etc, the file structure becomes a hindrance to me in regards to music. I started using MC for music well before images and video were useful to me in MC, so I think about music very much in tags, so there's nothing I gain from layers of folders.
As was stated earlier, it's super easy to rearrange the file structure by using MC, but I don't want to have to dig thru folders looking for how I might have filed something long ago. the fewer folders I have to traverse, the happier I usually am.
Other media types need that structure though, as it's harder to pinpoint the basic fields you'll always want/can search by.
Regarding Video, I'm using MC for everything but the actual recording of TV, and do have several subfolders in V:\ (Videos), including Movies, Documentary, etc. Since rock solid video is a recent (much appreciated) development, I'm still using what I used for the other programs I used to use for Video and TV, etc. I suppose once I have the time to really delve into theaterview setup/customization, I'll care much less about these subdirectories, and they may disappear one day too.
Regarding Images, I don't have them tagged well enough to use something similar to the above, it's mostly keywords, so no way to really have meaningful names that can be easily searched in windows explorer, so subfolders are a must for images.
I use this, for example, but I suppose it'll be hard to find a consensus on this
P:\traveling\mexico\estadodemexico\villaguerrero\totolmajac
I suppose the idea for me is *where* it was taken. I suppose that's the easiest way for me to know where to start digging thru folders. I'm sure other ways work well also.
Regarding Documents, I also have these in subfolders, but usually not more than one deep; Manuals, Health, Books, etc. the search makes is fairly easy to find most stuff; mower, diet, etc is usually sufficient for the amount of documents I save.