Yeah I wonder how big a part this plays.
I think another issue with the online is people hording humanity. I assume this will work itself out in time, but I've heard several different people mention playing the game only hollow. Not enough incentives to be human or people don't understand how the online is basically dependent on being human =/
I personally never sought out online play in Demon's Souls but it happened from time to time just as a result of frequently becoming human. In Dark Souls I'm still sketchy on how important and and rare humanity is, and I really have no idea what the benefits of being human are so I rarely change to human form (once in about 15 hours of play to be exact).
It would seem that it being so easy to stay undead takes a lot of players who aren't looking for online play but would do it if the opportunity presented itself out of the online pool.