Now someone please correct me if I am wrong, but technically, the difference between a blues and a ragtime not only has to do with the "feel" of a piece but also it's length and structure. A blues is typically 8, 12 or 16 bars. A ragtime has no such structural restrictions.

I know someone is going to say that a blues can be any length, but I've been told, technically (and I emphasize technically) that in order to be considered a blues piece it must adhere to measures I mentioned above.

Maybe a musical scholar could clarify if this is really the case.