Chris, Have you ever read yahoo/google TOS?  Any images you post via them they consider their property to use or alter as they wish.  That is why I don't post photos to their accounts or associate accounts.  I do post some pics to Facebook but I always reduce them to no larger than 800 pixels.  Even lowering the resolution does not always work.  I posted a photo on FB and 4 days later I saw it on someone's desktop image.  grrrr.  

At least rendo has plainly posted copyright notices and they offer the artist a choice to use an image freely or not.