One thing that was very much anticipated in the Nexus S and Gingerbread in general was NFC (Near Field Communication) support, which is a feature we've never seen before on an Android device. In fact, the vast majority of us took it to mean that it will allow you to use your phone as a credit card, which would indeed be very exciting and insanely cool. Unfortunately, that's not the case here; rather, the technology will allow the Nexus S (and other NFC-capable Android phones) to act as a glorified barcode scanner of sorts.
We first discovered this yesterday by way of page 333 of Google's own Gingerbread manual, which happens to mention that the NFC support built into Gingerbread basically allows phones to function as readers, but not as transmitters. Therefore, NFC-enabled Android devices will be able to scan NFC tags, or transmitters, but will not be able to transmit information themselves. In English, that means your shiny new Nexus S won't be able to act as a credit card due to the fact that it can't transmit information for NFC readers (potentially ones such as cash registers) to pick up on.
Andy Rubin then confirmed this at yesterday's D: Dive Into Mobile conference. While demoing the Nexus S, he pulled out a piece of paper which contained a "printed equivalent" of what was on his phone, scanned it, and was presented with a YouTube video. Cool, but let us not forget that this is essentially what you can do today with a barcode-scanning app such as Barcode Scanner or Google's own Goggles, only without a camera.
I'm not saying we won't be able to swipe our phones at the cash register instead of swiping our credit cards eventually, but what I am trying to make clear here is that we won't be able to do this with Gingerbread phones. For that to happen, Google would have to allow manufacturers to use NFC tags in their devices so that other devices could read information off of them, much like credit card readers do to credit cards (and also much like the exact opposite of what's going on in 2.3). Maybe in Honeycomb...
Update by Artem: I invite all the naysayers to read the official Gingerbread NFC API docs (and specifically NFCAdapter) - nowhere in there does it mention transmitting of tags. While the chip may support it, the API in Gingerbread does not, and that's the topic of this article.