First off, NFC doesn't really look for the bump. You don't actually need to touch the phones together, and the accelerometer is not used. The range is very short (like I said, about an inch or less, between my phone and my tablet ~1cm seems about as far away as they can be) so for the purpose of telling people who have never used it, it's easier to just say you need to tap the devices together. NFC does not use much power so you can leave it on all the time. (This is part of the reason why the range is so short, if you were generating a large enough field to power a passive tag from a few feet away, you'd kill your battery really quickly.) I may get this wrong but my understanding of it is that your phone is obviously an active NFC antenna (can send/receive and initiate connections) and there are also passive NFC antennas (basically RFID, you see these in NFC enabled posters and stickers).
Passive NFC needs to be powered wirelessly by an active NFC antenna. Again, this is why the range is short. The active antenna induces a current in the passive antenna with a magnetic field, and this gives the passive antenna enough juice to chirp back a small amount of data. This is how things like RFID entry badges/keycards and tags work, too.
Passive NFC can be used for obvious stuff like putting URLs on posters and stuff. But I've seen
NFC stickers for sale that some people use to automate tasks. For example, maybe you put one on your desk at home and when you rest your phone on it, it autoconfigures itself to turn on wifi and and silence all but emergency calls from your work.
Anyway, a lot of the problems you talk about (not being able to tell if it was tossed in a bag vs. pairing with the printer, etc.) are all problems that are solved by the short range. It's also convenient to not have to turn things on and wait...that's the exact problem that NFC is trying to solve. All you need is for your phone to be unlocked with the screen on (and I have seen hacks that disable even that, leaving NFC on all the time but that seems like a bad idea to me) and you're ready to receive. Want to send something? Go into the app you want to send from and then just hold the phones together.
Wi-fi Direct is a standard:
http://en.wikipedia.org/wiki/Wi-Fi_Direct
It's built into stock Android 4.0 (Ice Cream Sandwich) so pretty much any fairly new Android phone can use it:
http://developer.android.com/about/versions/android-4.0-highlights.html
See, I think this is what makes NFC cool. It's low power enough that you can leave it on all the time, and it eliminates a lot of steps (confirmation dialogue boxes shouldn't be necessary because both screens are unlocked and you need to get within an inch of the other phone, which would be hard to do without permission, and autolaunching a game on the receiving end is totally possible because it's on all the time).
