I haven't posted one selfie, ever, and I've been online since the nineties. I'm more concerned about showing up in other people's photos though. And you can't avoid that. You could ask politely not to be included in a photo, but that could be controversial, and I'm not about to go all Snowden on people and proclaim I have digital privacy rights which are un-enforced and the only way to avoid that is to be non-compliant in the various data-mining operations of Google et al. and have a 'rant'. Most of the time I waive my rights and be silent since it's more social and accepted.