Decided to try and help a random player through one "stint" to a Great One. I put my sign down at the bonfire leading up to the Covetous Demon and was picked up by someone called "Robertus", an American fellow with a pretty stable connection. He was my charge from here on out.
Went through & defeated the Covetous Demon, teleported to the following bonfire and dropped my sign. Ten or so seconds later, I was picked up by Robertus! "Excellent" I thought, "I'll be able to help him kill Medusa's sister too, I wonder if he realises what I'm doing."
Ran it through, defeated her and carried on. Dropped my sign for the Iron Keep bonfire and got picked up by someone else, was rather disappointed but sadly got killed trying to save this host's life. I dropped my sign again, hoping that Robertus had taken a break. Next person to pick me up was indeed, my charge.
Long story short, I helped him defeat the Smelter Demon & The Iron King. It was a weirdly fulfilling experience to be able to be summoned repeatedly by the same bloke and help them get a Great Soul, some bloke I didn't actually know, some bloke who picked me up for a third time and realised I was literally doing it to help him through.
Thought I'd share.
Also, side note, E3 are currently showing some cinematography of what I can assume at this point is another Souls-esque game. From Software + Undead Dogs + Living Head + Giant Monster thingy lurking in the dark. Name came up as "Bloodborne". I guess this is "Project Beast"!