The actual definition of a meme is: meme
/mēm/
noun
an element of a culture or system of behavior that may be considered to be passed from one individual to another by nongenetic means, especially imitation.
a humorous image, video, piece of text, etc., that is copied (often with slight variations) and spread rapidly by Internet users.
Therefore I expect them to do it. I would be flattered if someone felt my memes worthy of "stealing". If Something is good enough to share then I have accomplished my mission. I will say, sharing, reposting (what ever you want to call it) is one thing, actually claiming someone's work is another. At any rate, let them share. Holler if you see one of mine circulating.