What is its importance in your Facebook account?
I find it similar to a smile exchanged with your colleague whose recognition is limited to the similarity of your company’s logo on your id cards. In the virtual world it is half as effective. In fact, I think it is rude.
What you essentially say with a poke is that you want to stay in touch but are just too busy for a ping/message/call.
If this feature was not around, I would have pinged/messaged my friend (who lives in the same city) and probably met her by now.