I think that individual responses are better.
If the editor comes in to work on monday to an inbox clogged with angry emails from people who say they won't read the magazine again and are also contacting the advertisers it will have more effect than a one polite group emial. JMO.

ETA - since I'll never bother buying the mag can someone tell me some of the advertisers so I can email them
didn't think of it like that Chloe

maybe i'll send one from each of my email addresses - just to frustrate them - i'm sure i can find three ways of telling them how furious i am!

I THINK if you go to their website it has some of the advertisers on it - woolworths is the major one (they bring out the mag)...