As an iOS user, I always assumed QR code reading was just built into Android's camera app. Is that not so?
The AOSP camera app does not support QR code reading, and neither does Google's camera app. Many Android phones will have one or both of these installed. Most phones also come with a manufacturer-specific camera app. I know new-ish Motorola phones will read QR codes, and I suspect that the "kitchen sink" vendors like Samsung would as well.
Google Now has QR code reading built in, if you have a QR code on the screen (e.g through a camera app) you can have google now scan the screen by holding the home button.
I don't remember having to enable it, but if it isn't enabled for android users you can go into Google Now settings and enable "Screen Search".
You need to get 1 out of 100 applications from the app store, that competes for the one who can shows the most ads and be the least effective at decoding the picture.
Are you saying that the iPhone camera can read QR code out of the box?
The ZXing Barcode Scanner doesn't show any ads. IIRC, they give it away for free because they want people to use their (open source, natch) barcode library. I've been very happy with it.
This of course demonstrates a problem with the App Store model: neither Google nor Apple has a strong incentive or interest in directing users to the best, most secure, most privacy-preserving apps (particularly Google, who would prefer that privacy become a thing of the past): they would much rather that you buy something, or use some ad-ridden piece of nearly malware.
No, I meant that iOS doesn't have any built-in apps for it, so I always assumed Android must since QR codes are so prevalent.