I was inspired by this thread to do some research into
lulzography
Here is the evolution of Lulz as far as I was able to determine.
lol
lols
lolz
lawl
lawlz
lul
luls
lulz
epic lulz
Some contrasting data here leads to a few different conclusions:
1. Lul and its derivatives (luls, lulz, etc) are simply a corruption of the abbreviation Lol, from the phonetic Lawl.
2. Lul and its derivatives are in fact their own abbreviation for Lame Uncomfortable Laugh.
3. There are also a few altering views on the derivatives. Generally the -s ending (lols or luls, interestingly there is no officially recognized -s form of lawl) is recognized as a plural form of the base, while the -z (lolz, lulz, lawlz) is a more "spunky" variant of this plural form. Alternatively, the -z ending may also stand for "zebra", which would give Lulz the possible interpretation, "Lame Uncomfortable Laugh, Zebra".
It is generally accepted however that lulz are the one and only good reason anyone does anything, leading to the popular phrase "Did it for the Lulz".