I think that people who come to HubPages from other sites, such as Digg and StumbleUpon, where people are allowed to do that, might take it for granted that they will not be considered annoying here either if they share their links. There might not be necessarily an agenda behind sharing a link to a Hub, just perhaps, enthusiasm about a topic or something, but since everyone might not react favorably to such a choice of action, I would not do it if i were you. Stumble and Digg your posts, encourage your Facebook friends to visit your Hubs, there are many ways to promote yourself that are totally harmless. . .and will not get you in trouble,
Wish you well!