My warrior is running around questing and starts a group for an instance. I invite some people, and then someone freaks out about my health. Most recently someone drops the group without saying anything. He joins, asks my spec, I say prot, he leaves. I ask why and he says I only have 8k health.
Public Service Announcement: Most people solo in DPS gear, not tanking gear. Don't judge a tank by his soloing gear. Even my paladin uses a modified set with slightly less health for AoE grinding.