[petercooper]

People see the coupon code box and immediately head to Google to search for codes.

If your system would still benefit from a discount code and you're not selling low margin products, it's a good idea to "seed" those discount sites with permanent codes for very minor discounts (even just 4%, say). People feel like they've had a win even when the discount is minor.

[benmorris]

I've experimented with this. It is difficult to measure if I'm giving away money unnecessarily or completing a sale I'd otherwise miss. Good point though.

[jstarfish]

It depends on your industry and customer base.

When I was working with one that was primarily female and cost-conscious, that trick worked great. The fact that a code existed helped drive organic referrals (the code alone was enough to route traffic to me instead of a competitor).

Don't make it permanent or you definitely are giving money away to Googling cheapskates. Change it often-- people are excited by novelty anyway.