Surely these sort of rides have been happening for years, you just need to be ‘in the loop’ as it were. Loads have been put together on STW . Social networking, various ‘groups’ on the likes of Faceb00k, work groups, etc., all arrange get-togethers of various sorts. It’s already happening.
The commercial events (I know they’re not necessarily all profit making endeavours) become focal points in the yearly calendar for a lot of people but take a lot more organising and have a lot of legal niceties to consider.
In both cases all it takes if for someone to undertake to do the organising, however formal/informal 8)