A Dialogue Between Men of Letters: “Lots” of “Fun”!
Xah Lee wrote:
a very fun exercise. …
Peter Moylan wrote:
Since you're cross-posting this to alt.usage.english, it's worth pointing out that we don't say “very fun” here.
Xah Lee wrote:
very means like “very much”. Fun means fun. You don't say “vary fun”? Like, you mean varing degrees of fun or vagaries of fun but you don't say it? Or, but you write it and speak it?
I know not what it means.
“Fun” is a noun and most English speakers object to it being used as an adjective, and even more to an adjectival intensifier such “so” or “very” being attached to it.
Unless you couldn't care less about English usage, as a native speaker you would write “so much fun.” Your example would have to be amended, too, but it's a little harder to find an alternative that does not require more words (maybe this is a reason for accepting such monstrosities, but I still don't like them). I would suggest:
“a very enjoyable exercise”
“an exercise that was lots of fun”
thank you Stephen for your kind explanation but inline with alt.usage.english spirit and kind return to Petere Moylan, i object to the use of “lots” because it's contrary to the style in my book. 
lots has lots of meanings like a meaning lot, the pedantic lot, almost chosen by lot. When we are in the lot where lots meanings are allotted in lots of ways like lottery, it's a lot of trouble to decipher, and is not fun, despite lots of right in front.
 Lee, Xah. The Writing Style of Xah Lee
Athel Cornish-Bowden [acorn…@ifr88.cnrs-mrs.fr] wrote:
Look. Are you interested in English usage, or not? If Peter says we don't say “very fun” then we don't say “very fun”.
… my writing is razor blades in hot buns to grammarians, chocking dagger to mouthing moralists, logic bomb to irreflecting morons, eye opener to epochal theorists, immaculate calculus to logicians, euphoric oxygen to English masters, orgasmic honey to poetic chicks. That is to say, when i wanna be on the right occasion, too.
you see, English under me is like a love slave. I say jump and she jumps, I say kiss and she kisses. And when i need to vent, she bends double and pleads cum. Of course, it is not to say my theories are unerring or i'm impeccable or sans foibles and grammatical trespassings. But all things considered…
it is often the case,
that i do contemplate,
the degree of cockiness,
that i should exhibit myself.
if showing-off too much,
i then beget revulsion.
if i show not enough,
then i'm not man enough.
therefore i trounce,
when being pressed,
on the delicate balance,
that i might have trashed.
now you understand,
'tis not my loftiness,
but my frailties,
that you should endorse.
on the other hand,
with regard to the universe,
my name is Xah Lee,
and i'm still matchless.
— Xah Lee, 2004
This is originally a thread in newsgroup “alt.usage.english” (2011-07-19) At http://groups.google.com/group/alt.usage.english/browse_frm/thread/bdcae51e26338e8e#