Firstly, you're eating up your margin for error. This seems fine when you're scanning with an iPhone 4 from a galley proof in a brightly lit office, or from your calibrated monitor. It becomes a big problem when users are scanning creased newsprint on a poorly lit train, from a dirty TV at the wrong aspect ratio, or with a crappy cameraphone with a scratched lens.
Secondly, you're pissing away the inherent call to action in a QR code. Many of these more styled QR codes are barely recognisable as such. Either you reduce your scan-through rate because people don't know that your multicoloured blob is actually a QR code, or you have to explicitly state "this is a QR code, you can scan it". I hope I don't have to explain why those are bad design outcomes.
If you hire designers, this is a brilliant litmus test. Anyone who thinks that this is a good idea is incompetent, plain and simple. They will make decisions which are pretty, but will annoy your customers and cost you money.