[teh_klev]

Don't get me started on "could care less", my eyes sting when I read that. My other pet hate is "so fun", as in "that was so fun"...I blame those US kids channels for that one.

[jameshart]

Why is 'so fun' so wrong?

Fun can usually be substituted freely for a word like 'entertaining'. Is there something wrong with saying "That was so entertaining"?

[teh_klev]

Because "fun" in that context is being used like a countable or mass noun, therefore "That was so much fun" would be the correct usage.

"Entertaining" is an adjective and you can use "so" as a modifier to express how entertaining whatever you were doing or watching is or was.

This probably explains it better than I can:

http://www.grammarphobia.com/qa#a31

[jameshart]

Fun also functions as an adjective. "That was a fun movie. It was fun. How fun? So fun."

I agree, there's definitely two conflicting usages here: and activity can be the noun "fun", in the same way that doing something can be can be "bliss" or "hell" or "a complete waste of everyone's time". And so while I can say "My drive in to work was hell", I can't say "My drive in to work was so hell" (because not an adjective). But if I can say "My drive in to work was enjoyable", and even "My drive in to work was so enjoyable", then what's wrong with saying "My drive in to work was so fun"?

[jack-r-abbit]

I had no idea that fun was not allowed to be an adjective.

[eridius]

I assume the issue is with the construct "so fun", not the word "fun". And in that construct, the word "so" is an intensifier. It emphasizes the nature of the next word. You'll hear it in constructs like "that was so cool", or "that was so awesome", or other such phrases that kids like to say when they're excited about something.

[jameshart]

Kids like Hamlet: "So excellent a king, that was to this Hyperion to a satyr; so loving to my mother..."

[eridius]

Good point. My comment left the impression that it was something only kids say, but it's absolutely not. "So" is a perfectly good adverb that's used elsewhere as well. It just happened that the immediate phrases that popped into my head were things kids were likely to say (probably because the grandparent comment referenced "kids channels").

[jamestnz]

I think it's because some people and style guides (e.g. Strunk & White) reject this use of "so" as being a generic, overly vague intensifier. Often these people suggest pairing it with a "that" clause, which allegedly makes it more acceptable.

So, instead of "so fun", some people would prefer that you write e.g. "so fun that I squealed with glee", or even just "it was incredibly fun".

At least that's the argument I've come across. To the extent I even think about such things, I couldn't really care less if people use "so" like this; the meaning seems perfectly clear.