[matthewsimon]

The Guardian's UK stylesheet calls for this treatment of acronyms that are pronounced as a word -- people say "Icann", not "Eye See Aye En En" -- which does seem odd but may be acceptable as a regionalism.

[akira2501]

Some people make the following distinction: when pronounced as a word, it's an acronym. If it's not, then it's an initialism.

[T-hawk]

Some take the distinction further: only if it forms an actual word, like PATRIOT Act, is it an acronym. If it's pronounced but not a word, like NATO, it's an abbreviation.