There are a number of well documented problems with certain types of 'fair trade'. It can be over-rated - ask how much of your overpriced Green & Black's chocolate actually goes to cocoa farmers, ask how much manufacturing or processing is based in developing countries, ask whether 'fair trade' co-operatives are any better than local monopolies.

In terms of why it stays out of the mainstream, there is a real question mark over whether 'fair trade' principles can survive mass scale production. Moreover, market economics drive prices down; the 'enlightened' consumer has yet to reach a large enough mass to dictate the market. Consequently, fair trade will never be mainstream unless there is a significant consumer shift in putting principle above price.

From a more radical perspective, fair trade is a counter-movement and defines itself in contrast to the mainstream. Can the fair trade movement accept a culture change? I recall the furore over Starbucks launching a fair trade line. Some criticism was justified, the rest was just belly-aching that someone like Starbucks could 'co-opt' the name of the fair trade movement.