one thing that i never really took the time to check out was blizzard's new armory. normally i use it mainly for gearing and PVE purposes, or to check reputations and stats. however, i've discovered it can be quite handy for vanity fact-checking too! (months behind, i know :P)
i often get asked "so how many pets are you up to now?" and sometimes being a bad collector, i simply cannot remember (for shame!) and need to check WarcraftPets for an actual number. well if that website is ever down (heaven forbid), now i have a back-up source on the armory. yay? lol.
for those who are curious, simply go to any toon's armory page, and on the left hand menu there is a "statistics" link. once on that page, go to the character page and finally "gear". vanity pets and even the number of mounts owned can be found on this page. :D
side note: i found it strange that the number of vanity pets a toon owns is listed under the "gear" section. i guess technically we could "wear" our pets? a westfall chicken sitting on top of my head would be slightly uncomfortable though.
this is a really useful tool, especially for those who wish to accurately track the stats of friends/other players. it also makes deceiving collection websites such as WarcraftPets and Warcraftmounts a little harder to do. still not foolproof, but there really is no such thing as a foolproof system/method imo.
on the other hand, it does bring up the question of privacy/transparency. some just don't want others to know that much about their characters, so rather than a useful tool, it could be seen as an invasion of a character's personal stats. it's hard for me to see how this non-gamebreaking, vanity information could be used maliciously against another player, but people have found ways to harass others with almost any type of information so.. i wouldn't put it past someone to do so.
it has it's pros and cons, although at the moment i'm seeing more pros than cons. i can check up on guildies, friends, and most importantly... my alts! although i don't actively collect on any other character than my main, it's still sometimes useful to know how many pets an alt has. it doesn't give me detailed information such as WarcraftPets would, but it's a start if i just want to quickly refresh my memory of how many i've collected on so and so.