The Developer Edition trend started with Motorola and then Samsung, as their alternative solution for making people who wanted an unlocked bootloader, happy, while they couldn't convince carriers (or didn't try hard enough to convince them) to allow phones with unlocked bootloaders on their network. After trying to release codes to unlock the bootloaders of many of their phones, HTC is joining this unfortunate trend, too, with the HTC One.
Why is it unfortunate? Because it's not a real solution for people who want to buy phones and then unlock them. Most people (at least in US and Canada) buy their phones with a contract and subsidized. But at the same time many of these people will want to unlock their bootloaders and put custom ROM's on their phones to extend the life of their devices, considering the companies themselves give up on these phones much earlier than the developer community.
So now the companies joining this "Developer Edition" trend are taking that away from them, unless they are willing to pay $650 upfront for an unlocked phone, which is what HTC is going to charge for the Developer Edition of the HTC One. Unfortunately most people are not going to buy these phones unsubsidized, unless they are really developers.
In the same time I'm hoping that something good will come out of this. With T-mobile giving up on subsidizing phones and planning to sell only unlocked phones (for much cheaper contract plans compared to their competitors), and with hardware getting "powerful enough", even for lower price ranges, for most people, I could see a new trend rising with people starting to buy these unlocked and unsubsidized phones, instead of being stuck with contracts for 2 years.
It could also be a lot easier if all networks switched to LTE completely, and modems started supporting all the LTE bands, so you could easily switch between carriers, too (at least if you go the pre-pay route). So maybe this Developer Edition thing will play a part in convincing people to stop buying subsidized phones that are locked to the carriers' networks. But this will only be true perhaps in a few years from now. Until then, most people are probably going to continue buying the non-Developer Edition models.