Um, where precisely. And am I invited?
You are right that language grows and develops. But in this case, "irregardless" was entered into dictionaries not because it was a new word, communicated something other words couldn't effectively communicate or was some folksy slang that became accepted. It clearly was used by idiots that didn't understand how to use "regardless" and/or "irrespective". It may be listed in the dictionary, but is usually described as a something that is NOT accepted as proper, and shouldn't be used. Take this definition for example:
http://www.merriam-webster.com/dictionary/irregardless?show=0&t=1284695819
I can see it now, the definition of "mute" will expand to include "of little or no practical value or meaning; purely academic" because so many freaking idiots don't know how to pronounce "moot".
My favorite dictionary is The American Heritage Dictionary. They have a usage panel "consisting of around 200 prominent members of professions whose work demands sensitivity to language." For controversial words they tell you what percentage of the panel finds a particular word, or use of a word, acceptable. Very interesting, really. For what it's worth, The American Heritage Dictionary's online definition of "irregardless" (without Usage Panel info) is:
http://dictionary.reference.com/browse/irregardless