I have a habit of losing track of how well I'm articulating myself when I speak, but it turns out that I'm definitely not the only one. For some reason, I have always been hugely amused by the ambiguity in language, and respond to misinterpreted words with embarrassing fits of laughter (like how my sister always thought NPR's Bob Edwards was Bob Backwards.) I just hope no one interprets my amusement as language snobbery. I don't think these mistakes are dumb - I think they're kind of brilliant, and give insight into how people think about language.
I noticed how lazy I can be about articulating myself soon after I graduated college and started working closely with a woman who'd grown up in China. She was a great phonetic speller (which I imagine is true of most people who grow up speaking Chinese) and wrote down exactly what she heard people around her saying. To Xun, Anthrax was antruas. This was about ten years ago, and I've slipped considerably in the interim.
I have to wonder when being inarticulate becomes an accent or dialect in itself.