this is a really good topic, it's a pity we haven't seen more posted up from others.
I agree with random, sometimes the lack of spontaneity can keep me disconnected within this type. I think also, our quietness and the levels of verbal communication that people misinterpret for judging/shyness/snobish-like-attitude also arises as a problem. I think our ability which is both a gift and a curse in itself is our ability to manifest/mirror whatever the person we're talking to is thinking - so we can often put on a mask so to speak. I read this from a great blogger, i've forgotten his name but he wrote it a little while ago so i can't take the credit, it might help to explain what we are like though in this circumstance (and what i'm finding so hard to say):
The Method Actor
“Everybody knows you never go full retard”
This one right here, my friends, might just be the reason you INFJs have been documented as the rarest of types. Oh the power of the persona, when you project and image, people will create your identity based on that image, regardless of what is actually going on in your head. This marks an extremely uncanny ability that you INFJ folk have. The INFJ can invent an character within their Ni-Fe. They can write an entire story of their life, their family, their experience, their fears, their motivations, their quirks and mannerisms all within their Ni. Then when the time comes, then can channel that character into their Fe and Se to perfectly embody that role, in ways that can be so nuanced that you might not even know you are looking at the same person. Even if acting isn’t your thing, every INFJ still has this in them, and it often comes out in other ways. An INFJ could enter a completely foreign country, and within weeks, or even days, completely master their culture, and maybe even accent.
Fictional Examples: Song (M.Butterfly), Kirk Lazarus (Tropic Thunder)
Real-life Examples: Sasha Baron Cohen, and anyone who can properly play the Master of Masks prestige class in Dungeons and Dragons.