Maybe you have sen them all in other galleries, but then it's titled as his favorite, so it's just an organization of the pictures he liked the most from those galleries, making it unique to the poster. Now, if he posted up the exact same gallery as someone, or added like 2 pictures and called it his own, then there would be a problem. Unless you post something that just came out, it's hard to post anything without someone who has already done it, so "Personal Collection" galleries are the only other route to go really.