Or... if you just type in WOW macro on google, you can see about 100 websites that already have a million macros. Why reproduce what someone already does better then someone who doesn't do it?

Adoul, those 100+ websites with WOW-macros don't always have the usefull information one needs (though wowwiki is a good place to start) and some of them are overrun with idiots spamming XXX-rated websites.

This particular macro is simple to read, even if you've never written a macro before, and it helps to understand them for people who've never seen programming code:

/run CallCompanion("CRITTER", random(GetNumCompanions("CRITTER")))

reads as :
Run the CallCompanion routine, use the category "CRITTER" and the index of the companion in this category, is a random number from 1 to the number of companions I have in the category "CRITTER"

I rather read one good written macro than 100 bad ones that are posted with a "plz help fix this" at the END of the entire post ;-)

Also, I believe the macro interface saw significant changes in WoW 2.0 and 3.0; if somebody wrote a guide back when the level cap was 60 and couldn't be bothered to update it, there's a very good chance those macros wouldn't work now. This would be particularly true of pets and mounts, since they're now treated more like spells rather than items.