Here's what I said in another thread about the subject:
Cool! I'll share what it's like from the other side of the road:
One of the main reasons why ESTps need INFps is to warn us of any stupid shit that we're about to do, and talk us out of it. This is because when ESTps think of something funny to do, they usually immediately act upon it, without thinking it through first. The ESTp is comfortable enough with the INFp that they can share with them their thoughts. Then, the INFp steps in, and tells them that what they're about to do is pretty damn stupid, and it'll make people think less of them, etc. The ESTp will realize the error of their ways, and not act upon them!
Also, the INFp often times knows how to think up of things to do that won't get us into deep shit. When they tell this to the ESTp, both become all happy, and the ESTp provides the means to turn these ideas into action. (A prime example of this was when my INFp friend and I were on the Ropes Course. He'd be like, "Ooh, let's do the Ships' Crossing, the Multi-Vine, and the Dangle Duo together!" I'd be like, "Sure, that sounds great!" and then we'd go off to do the climbs. While doing them, he'd tell me what obstacles were coming up ahead, and then I'd figure out how to get passed them. We were a great team!)
Another thing that ESTps enjoy about INFps is how they seem to be completely at ease with them. INFps have their crazy imaginations, and aren't afraid to show them off to the ESTp. For example, just seeing an INFp pretending to play the drums while listening to their iPod, or acting like James Bond, you name it, is enough to make any ESTp all woozy inside.
Many people say that INFps are passive, like it's a bad thing. However, in the eyes of the ESTp, it is not a bad thing at all. I can't really explain it; but this "passiveness" of the INFp is quite adorable, actually. ESTps can find it quite sexy, given the right situation. :wink:
This is just the beginning. If any INFps have anything to add to this, from their perspective, by all means they should do so!