Social event, fine, so why deliberately hold up other road users? The twenty milers, Spokes rides, the Edinburgh Fixed Gear lot, The Bike Chain store all have social cycling events that do the same without antagonising... CM certainly doesn't have a monopoly on being able to cycle in a social environment and get to know people, and for me don't have the drawback of intentionally causing an obstruction.
they took up the entire lane too and rather than get annoyed I thought "cool" and "way to go"
I'd hazard a guess at this reaction being because you're a cyclist.
As for CM making cyclists 'visible' to drivers I guess that's a point for some research. Personally I don't think that a driver being 'held up' by cyclists in the CM way will make them notice or act any differently to cyclists in the days afterwards - but I realise I've got nothing to back that up save for gut instinct so I certainly cannot state that as fact.
It's certainly ironic that cyclists are seen (in general, as well as at CM) as causing an obstruction when the sheer weight of motorised traffic will hold them up far more regularly and for longer.
Incidentally, the film on the origins of CM (the name of which escapes me) showed very well how it started as a true celebration of cycling. There were still people who got annoyed, naturally, but they had ways to try and turn that anger into laughter in many (stopping traffic so the cyclists could cross an intersection with carboard signs saying 'Stop', which when the horns started were rotated to reveal 'Honk if you love bikes' on the other side). Some CMs now seem to revel in the mid-ride 'stop in the middle of the road and lift your bike over your head' thing, which has nothing to do with making the cyclists on the ride safe, nor endearing themselves or cycling to those around...
I have a feeling there's going to be an agreement ot disagree on this one. Basically, if I want a social ride I'll go on one that doesn't annoy other people.