Is it appropriate to treat "FYI" as a noun?

Since FYI stands for "for your information", I would tend to use it like this:

FYI, I think the fish has gone bad.

In other words, the acronym simply replaces the phrase. However, I've heard FYI used many times in the following way:

As an FYI, you shouldn't mention his ex-wife.

Here, it is being used as a thing. This doesn't quite sound right if you fill in what the acronym stands for. It's as if a for-your-information is taken to be an object in a similar fashion to a(n) FAQ.

Anyone have some insight as to whether the second usage above is considered valid?

Using FYI as a noun is perfectly normal and common in business. "As an FYI, check out today's report on sales," is the sort of thing you hear all the time. "He sent me an FYI on that" is unobjectionable.

Personally, I find it awkward to use FYI as a noun. I read FYI as "for your information" in my mind, as oppose to "F" "Y" "I".

So when I see "As an FYI" I read it as "As an for your information" , which is wrong.

I guess it would sound okay to people who actually say "F" "Y" "I".

This is also seen in other short forms, like ASAP, LOL etc. Some pronounce it by the alphabets, some pronounce it as a whole word.

I would tend to think that short form like these in itself indicate a loose grammar. You would not see FYI, don't, ASAP, IMHO in an academic paper. In places where you are likely to see these short forms, I think it is acceptable to use it as a noun, since the grammar is not as strict.

Lastly, it also puzzles me why people write "As an FYI, we will be out of business soon" while they could have simply said "FYI, we will be out of business soon". Not only providing the same meaning, but also saves a few keystrokes on the keyboard, and is grammatically correct.