A name is just a trademark, but a logo is a work of art, and may be covered by both trademark and copyright law. For example, the Debian/Firefox controversy hinged on the non-free copyright license governing the Firefox logo artwork:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=354622
Furthermore, the implication that words are trademarks and logos are non-trademarkable works of art is misleading. Names and phrases registered as trademarks are called word marks, and graphical logos are considered design marks. Both are trademarks (or servicemarks if you're offering a service).
This is a pretty useless discussion in any event. If you're wondering how to protect your logo, you should really ask a lawyer. All I'm saying is that your lawyer will tell you that you should trademark your logo, and that copyrighting it would be a complete waste of your time.
"Several categories of material are generally not eligible for
federal copyright protection. These include among others:
...
Titles, names, short phrases, and slogans; familiar symbols
or designs; mere variations of typographic ornamentation,
lettering, or coloring; mere listings of ingredients
or contents."
Every legally protected logo I've ever seen is trademarked either at a state or federal level.
You would only trademark a logo if you plan on associating it with your company and you don't want any other company to use the same or similar artwork in their identifying artwork.
You could trademark it and then license the trademark to companies that you want to allow to use it. This is pretty common. Some reasons I can think of for this kind of arrangement:
* Parent companies licensing their trademarks to subsidiaries.
* Unrelated companies using similar names who enter into an arrangement where one owns the trademark and the other licenses it. E.g. Tyco International/Tyco Toys, ITT Corp/ITT Tech, Apple Inc/Apple Corps (after Feb 2007).
* Certification, compatibility, or similar logos can be trademarked and licensed to authorized users so the owner can protect against the logo being used in an unauthorized or misleading fashion. E.g. UL Listed logo, Orthodox Union kosher symbol, Windows compatibility stickers.
* Franchising and similar situations. E.g. car dealers, fast-food restaurants, co-ops like IGA and Ace Hardware.
* Avoiding legal hassles that might ensue if the name/logo were not trademarked. E.g. Linux.
Images are copyrightable. It would never make sense to trademark an image because if you can put the image in a fixed medium a) it is free and b) it is protected much longer.
Copyright only lasts for a certain number of years (unless you're one of the people who thinks the government is going to extend copyright terms forever so Micky Mouse never falls into the PD...) whereas trademarks last forever if you can enforce them.
Logos are copyrightable, a trademark is stronger -- But of course, you can copyright a logo it's just an image after all and those are very easily copyrightable.