I've had this happen several times lately as well. The most diplomatic thing to do is to accept their request and then hide their news from your feed. That way the requests stop and your feed won't be cluttered with stuff you probably won't read anyway.

One other thought on this: fan pages should grow organically because a person or company actually has fans. Chances are if someone needs to beg their friends to become fans, their fan page is a temporary hobby (as opposed to a serious part of their marketing plan). I'd be willing to be that person that bugged you will have a neglected fan page in 6 months.

IMO, if page owners need to consistently re-send invites in a short insufficient time space, perhaps they need to rethink their page/product, or think about who they are targeting when sending invites rather than “select all”.

That being said, there is the “Ignore all invitations from this friend” under every type of invite, which avoids the awkward note to “friend” business. If they've defriended you for it, they've just taken the social out of social networking!

I receive a request to join a competing web developers fan page once a week but it's really something I'm not comfortable with. Sure I can keep up with their business news through it but I know they are the type to judge the success of the page by how many fans they have so I reject the request. Every week. It doesn't bother me. I spend every day clicking ignore on a few requests, from event invites to app requests.

If, for you, it's a case of an already full feed then join and hide it. All gone, no worries.

I understand why they unfriended you. This sharing is how they get value for their time on Facebook. You didn't want to be apart of that. I assume is person was barely an acquaintance. Instead of 2 little clicks with the mouse you took the time to write. I think you worry too much.