I agree with that, however I would consider large forums (especially those that arose after the rise of the Web- so not BBS- and those that were more than simply vBulletin/phpBB message boards) to be basically photo-social media, even if they predate the term and concept.
I think we need more forums outside of mega-communities like Reddit or even HN, but at least there are many that are still alive:
Also, things were going viral even before the mid-'00s when the concept consolidated. All Your Base and Star Wars Kid went viral before it was called that, even if they garnered a fraction of the mindshare of the general public. Even that dancing CGI baby qualifies.
That was the sweet spot IMO. The days before things were constantly "going viral". Sometimes memetic speedbumps are a good thing.