I've actually done this recently! The person was very nice and gracious even when letting me know the pet wasn't UFA.

I feel there is no hurt in trying, but to do so in a particular manner. - Always do so privately, I always make sure to ask in a private smail, that way I'm not openning the floodgates for them to be harassed or asked by other people who might stumble upon comments. - Always be polite. Be courteous and always thank them for their time even if I'm given a no.

The way I see it - the worst that could happen is I get a no and move on. Could be that individual might consider adopting out if they aren't particularly attached and know someone is eager to work and use the pet! Also I've found that people who don't want you asking for their pets will include a note on their profile making it obvious and saving you the time.