I don't care who you are; declaring yourself to be 10th Dan is bad form. Someone else has to give you rank, even if it's posthumously.
I agree, and I've never understood how someone can award you a rank posthumously...wouldn't that leave someone rather incapable of doing...well...anything?
Not only that, but I think what doesn't look so good is, for instance, a guy who wants to create his own style, that, for the sake of argument, actually has a valid reason for creating one. We'll say that he's doing a mixture of TKD, Kenpo, and several CMA's that he's studied for many years.
Well, out of all the arts he's studied, the highest rank that he's earned is a 4th degree blackbelt, we'll say in TKD.
How, then, is it that he can combine all his other arts and magically come up with 10th dan in his own art? How does one come up with the correct number?
Wouldn't it be more realistic to say that you're the teacher of the system, and that you're simply a blackbelt? You can instruct others to achieve a black belt in your system, but they would always be considered lower rank than you since they're your students learning your style. If you don't promote someone past the level of blackbelt, then you don't have to worry about what dan you are...just get rid of the dan system all together. I don't think they should be needed outside of the arts and systems that already employ that method, myself...and it would avoid all of the bickering about how "qualified" someone is.