Do you mean the people that give you free samples?  If I take a sample, I say Thanks :) 

Or are you talking about something else?

I always say Thank-you if someone gives me something- no matter what the circumstance is.

I'm like Meri... I say "thank you" when ever someone gives me something...no matter who it is.

I don't shop at Costco...I shop at Sam's.

I say thank you when people shove flyers and stuff into my hands even though I don't want them.  I don't thank the sample ladies because I don't eat grocery store or wholesale club samples.  I say no thank you and move on.

I try to but sometimes there's a hoard of people around the display.  I try to actually listen to them tell me about the product too, instead of just taking it and going.

We don't shop at Costco (we don't have a member card) but my family and I always say "Thank you" to the salespeople. :)

I always say "Thank You" when somebody offers me something.

I always say "thank you" if some performs a service or gives me something (something I WANTED that is!).  It's the right thing to do.  Things I DON'T say "thank you" for: Punch in the face, gun in the face, a cold, the flu, swearing, spit (unless I'm swapping it with someone I want to be swapping it with), spoiled milk,  tax bills and "the business".... there are more, but you get the idea.....

Thanks for the chuckle.