I love Geni, and I’m on the site regularly. Since they made me a curator, that’s only right, really. I have a job to do.
Since the goal of Geni is indeed to create a world tree, it is NOT a good site to keep your personal genealogy tree on. That tree you can keep in genealogy software (I keep mine on a separate drive, cause it takes up so much space), or over at a site like My Heritage — there you can keep a tree with your own information, your own documentation, your own connections, and you don’t have to put up with anybody else changing things.
Geni is a collaborative site, a very different thing indeed. Though it’s possible to have profiles made into what we call Master Profiles, which can then be locked — or to have profiles kept private, in the case of all living people, and people who are closely connected to you — in general if you’ve got your work up on the site, it can be changed by other users.
It can be a headache (sometimes other users have Very Different Ideas about what constitutes a reliable source), but in general I find the site very useful indeed for genealogical work. That’s because different users can bring in various sources. And we have discussions about how to interpret the various sources.
So the tree tends towards reliability.
And I do indeed love working in it.
Currently I am diligently working in the medieval Welsh tree, which is a problematic piece of the tree.
But if you’re on Geni, and you ask the curators to help you with a problem, you might run across me, being helpful.