Droid branding is Verizon marketing, no more, no less. Yes, George Lucas owns the copyright, Verizon pays him royalties to use it. Every phone that has the name gets the full Google experience and branding, but they only apply the name to certain devices. Mostly, it applied to devices they thought would be somewhat of a standout, they though would be a bit of a game-changer, etc. Look at the original Droid kicking off Android with style, the Incredible bringing us the 1ghz Snapdragon hardware and AMOLED screen from the Nexus1, and was one of the most powerful devices last spring. The X ushered in the idea of phones as a mini-tablet, and paired it with pretty powerful hardware for its time.
Yet the Droid name has been applied to a few flops as well. D2 and D2g were a definite step backward with their locked bootloaders, and the DX2 we all know to be a placeholder/copout until they can release the Bionic. DInc2 is a nice step up from the original, but isn't anything special these days, its pretty much a T-Bolt without LTE, so its a tad lighter and has better battery life. And let's not forget the Droid Eris, which launched alongside the original Droid. Verizon couldn't give away that restyled Hero, and remember it launched with Sense right alongside the vanilla OG Droid. It seems they'd rather you forget about it.
Originally they wanted to apply it to all high-end devices, while selling low-end and mid-range Android phones without the name. This is when Microsoft convinced them to sign an agreement to put Bing on all non Droid-branded devices, since they figured anyone who really knew or cared about having the Google experience would put up for a Droid anyway. But then more good phones kept coming, and they didn't want to crowd the offerings. That's why we had a few great devices miss out on it, especially the original Galaxy S/Fascinate, which DEFINITELY should have been a Droid, complete with support and marketing.
Not sure why the T-Bolt doesn't have Droid branding but does have the Google experience. Either the contract is expired (if so, why Bing on the Rev?) or they may simply have told Microsoft they were making an exception. The Thunderbolt certainly got a lot of marketing and support, maybe they simply didn't want to confuse the consumer by releasing an LTE device with Droid branding until they had time to market the idea of 4G LTE itself. This effectively puts the T-Bolt in the same "premiere" class as the Droid phones, whether it has the branding or not.
AFAIK, the Charge did not get Droid branding until VZW realized the Bionic would not be launching on schedule. Apparently they wanted to get a good Droid branded LTE device out soon after the T-Bolt, with a few improvements of its own. I'm guessing they chose Samsung over LG because they believed more in Samsung's ability to deliver a quality device, they figured it would be the most stable since it was based on existing hardware, and in a bit of a nod to the fact that they really screwed Sammy last fall with the Fascinate. The fact is, Galaxy S hardware still holds its own in today's market, and the Charge brings a better screen and camera than the T-Bolt, while the Rev is pretty much the same phone.
So maybe its not as revolutionary as the original Droid, but I'm still glad the Samsung got Droid branding. Its definitely the best of the currently-available LTE phones, and the most likely to be able to hold its own for awhile longer in the marketplace, considering it has a GS2 screen and camera and the Hummingbird is no slouch. Again, the original Fascinate would have been a great seller if it had proper support and marketing, and the complete Google experience. It seems VZW has finally realized that.