The post for June 10, 2009 over on Blog de Heráldica (http://blogdeheraldica.blogspot.com/) is a good one discussing the difficulties than can be caused by excessive rigor in blazon. To illustrate his points, the author uses two examples from Spanish heraldry: first of the growth in the number of serpent heads in cauldrons, from an original two (which were really just a decorative version of hooks for the handle to attach to) to four, to a whole bunch issuant from the cauldron itself; and then of the problems which have arisen from specifying the number of squares in a checky field.
I can highly recommend this article. For those of you who can read some Spanish, you can probably just pop on over there and read the article. For others, you might want to get a (_very_ rough) translation through AltaVista Translations (http://babelfish.yahoo.com/).