Hi Adam,
Yes it does put extra wear on the anchors (not a lot, but if everyone were to do it and the anchors are not rings then it is worse). I would imagine the main reason that the MCSA Meet Convenor did this was out of safety and convenience.
Safety point: The (I'm guessing mostly novice climbers) are unable to kill themselves i.e. they cannot un-clip anything. This takes a huge worry off the person in charge.
Convenience: When everyone is tired out, no one has to go and clean the routes, they simply just pull the rope. This saves (valuable) time and effort, especially when out with a big group.
I hear you saying "
but the anchors are getting worn down at a rapid rate!!". This may be the case, but in most cases they can replaced. If sport climbers contribute towards 'fixed hardware' for their sport then the anchors could simply be replaced with new ones.
To me the fact that someone was willing to take out 30 climbers is great (he/she is not being selfish with their time!). The MCSA contributes a good amount of time/effort/money towards our mountains/sport, in my mind it's ok if they toprope directly through the anchors
Obviously if you don't have a good reason to go directly off the anchors then please don't!