Months without responding to an email? Yeah, I would be annoyed. I think it's only natural. I almost always respond the day after, unless I know the person really well, or it's an urgent matter because I have this thing about not wanting to appear to eager.
I'd never put it off for months, tho.
If I come into contact with someone who has ignored my emails or calls, I'll mention it as soon as I see them. Something along the lines of, well, hey, where the hell have you been? I've been trying to contact you via blah blah blah for blah blah amount of days/weeks!!
How's about a bit of backstory, though? Depending on the situation, there's always allowance for personal matters and such... If it's someone I know doesn't use their computer or voicemail often, obviously it makes no sense to make a big deal about it.