My old Nokia xPress Music 5300 charged on 5V. It even had a mini-USB port to transfer data between a computer. However, it could only charge through the nokia-specific mini-pin connection, not the USB port. If the phone didn't use 5V, or didn't have the USB port already, I could understand using a proprietary connector. However, when the only thing missing is a connection between the USB 5V pin and the battery, I have a serious problem with companies using non-standard chargers. Needless to say my current phone uses USB, and I don't plan to switch back to anyone who doesn't.
However, this is sort of old news. If I recall, China has already mandated that all cell-phones sold in the country charge via USB, so the EU is simply following suit.