Actually, it *can* hurt to ask. My raiding toon is a level 80 holy priest. Even though she has a guild and says nothing about wanting to switch guilds, she gets bugged about switching guild on a continual basis. It gets very old very quickly.

If someone whispers me about being put on their friends list for future possible pugs, that's cool. If they start a recruitment conversation then that's a guild I will _not_ join since the people there are clueless about me (given I never, ever indicated I wanted to switch guilds).

That said, a general comment over vent and raid chat to your pug folks of 'Thank you for coming tonight. Please keep us in mind if things change for you" is fine. It's a nice touch and doesn't single anyone person out while opening the door for potential recruits to approach you.

I agree with Piper on this one, although I think it can be situational. Before I made my own guild, I would get asked after runs if I liked my guild. At the time, I did like my guild and found the question annoying. I know my former guild leader had to deal with the ire of some other guild leaders because members of our guild had asked puggers if they were happy. They returned to their guild and said, "So and so from this guild asked if I was happy here. Why wouldn't I be happy? Is something going on that I don't know about?"
And having been in a guild that was poached, I know how other guild members feel when they see people leaving because they have been promised bright, shiny things by another guild. Morale takes a tumble, even a little bit.
But, people come and go all the time. I've had, over the course of a year, probably a dozen people come, stay and leave because what we do and how we do it, isn't as appealing as they thought it would be. I don't look at those people as being "poached" so much as their needs have changed and they are taking a different road than us. But I would get irritated if one guild seemed to be contacting a number of people in my guild asking if those people were happy.
I hate Pugs. I've had more bad than good, but I will help a guild member try to salvage a run going south. I also have no qualms about bringing someone into a run I'm in, but I don't be the person in the LFG channel. I never mention that I'm the GL and I never say anything about the guild, even if the person is unguilded. I've found that the conversation always, at some point, unless it's the last boss fight, turns to your guild and the best "salesmen" are not the officers, but the "rank and file", so to speak. Once someone expresses an interest in us, then it gets pointed out that I'm the GL and can answer questions.
I have gotten a couple guild members off assistance runs, where I run some low levels through an instance. It generally starts with, "Thanks Gimm. That's the GL who helped us." "Really? Your GL runs lowbies through instances?" "Oh yeah! She does all sorts of stuff." Potential recruits always have an interview and must go to the web site, but you do score major points by being the GL who cleared Stocks for a group while wearing a dress.