If you came up to me and said you liked my avatar and wanted something like it, I'd provide you with files and guidance about how to do it.
If you came up and just took my avatar, yeah, I'd be a little mad with you. I understand that I don't own it and all that, but I did put time and effort into it. My avatars are all fairly heavily modified gamerips, so it's not like I just uploaded something I found on booth.