Scabble Players: What acronyms are allowed in Scrabble?

I know that the rules say that Acronyms aren't allowed, but there are some words that people forget are actually acronyms, like Scuba, Laser and Radar. Are these words legal or do they still count as illegal since they are technically acronyms?

I can understand things like NASA, and even grudgingly agree that TARDIS is illegal(though I'll always allow it), but words like Laser(Light Amplification by Stimulated Emission of Radiation) and Scuba(Self-Contained Underwater Breathing Apparatus) are much more common and less likely to be thought of as acronyms.

And yes, this came about because of a conversation about whether or not TARDIS is legal to play in Scrabble.

So: To the people who have played Scrabble competitively: Are any Acronyms accepted as legal words in Scrabble? Do we just have to use it in every day speech long enough for it to become a legal word or does it always count as being SCUBA and never Scuba?