The big one for me is image quality and metadata. Images shared in "mixed company" are lower quality and have the metadata stripped; it's not dissimilar to being sent a screenshot of a picture instead of the picture itself. It's not a big deal for "Look at how big the kids have gotten!" but if I go on a hike or beach trip with friends or family, and there's something they took that I care about, I have to say "Great thanks for sending but can you upload it somewhere else," usually Google Photos, and go through that whole dance.