The impression that I had got from reading JayBonci's original writeup a few months ago was that when you created a nodesphere, only nodes authored by you would be a part of it. Which would be neat, your own little metanodes. Actually had a few planned out. Perhaps less useful, in the cosmic sense, than the suggestions others have made, but probably infinitely easier to implement from a logistical standpoint.
Let's say I do a writeup of the Sleater-Kinney song Youth Decay. I include full lyrics and both sets of guitar tablature, and since I'm a good little boy, I also explicate like mad. Since this is such a lovely and useful node, I want to add it to a nodesphere, to increase its exposure and accessability. I'm kinda stuck, though, on where to put it.
My initial thought is to stick it in the Sleater-Kinney songs nodesphere. I get to wondering, though, where in the 'hierarchy' of nodespheres this particular one falls. Is it in Olympia punk songs nodesphere, which is then a member of Pacific Northwest punk songs, which is a member of Punk songs, which is a member of Songs? But shortly before the release of the album Youth Decay appears on, most of the band's members moved to Portland. Should Sleater-Kinney songs instead be a member of Portland punk songs? Neither one is really accurate for the whole of the material.
So let's say instead that Sleater-Kinney songs is just a member of Punk songs, and do away with all that geographical nonsense. But come to think of it, not all Sleater-Kinney songs are really punk rock - Jenny, for example. Maybe put it in 1990's songs? Nope, All Hands on the Bad One was released in 2000. So I guess we ought to just end up sticking Sleater-Kinney songs inside Songs. This is dumb. Since the writeup can only be a part of one nodesphere, we don't get to have Punk songs or 1990's songs or Female-Vocalist songs at all.
Even worse, if someone is looking specifically for, say, punk guitar tabs, they would have to sift through the whole list to find them, since my writeup can't be a member of both Sleater-Kinney songs and Guitar Tablature.
All this would be fixed by allowing membership in more than one nodesphere, which opens up a whole other can of worms altogether. I guess the point I'm trying to make is that if you're going to make this significant an addition to the functionality of the database, please try very hard to do it Right. This is not an easy problem, and could go badly quite easily.
I'm still quite partial to the personal nodesphere idea.