This probably belongs more in the project board or something, but I always enjoy seeing people slowly build up and assemble/paint their stuff. I don't think I have the money to pitch into starting a marine army of my own (although I have a soft spot for the Howling Hriffons), but I love checking out those types of threads.
And when one does have the money/time/inclination to participate, it's pretty fun (imo) to get to share your stuff.
Actually, if something like this was set up at a -super- slow pace, I might think pretty seriously about joining up. Especially if allies were allowed and it gave me a chance to fiddle with some IG or Sisters of Battle as well as marines.