I have a server with under 8 people playing on it. I was on by myself, made a Sojourner's Sash and equipped it, and I got the speed & jump buffs as expected. However, when other people logged on, they didn't have any baubles equipped, but they are also running faster and jumping 2 blocks high. When I take my sash off, they lose the effect. It seemed to apply to everyone on the server, we had 4 other people besides myself all getting the effect.