Coles' FlyBuys has recently joined Woolworths' Everyday Rewards in offering "activated rewards": deals which only apply if you click on a link to activate them and then spend a specified amount of money within a specified time frame. Lifehacker's advice on these remains unchanged: they're a good idea if they offer you a saving on something you actually needed to buy anyway, but not otherwise.
The most recent activation reward I got from Woolworths offered me 6 cents a litre off petrol if I spent $45 or more, 7 cents off if I spent between $60 or $69, or 10 cents off if I spent more than $70. That's not a bad deal: most households with two people in them would easily spend more than $70 on the weekly grocery shop, and 10 cents off a litre is a pretty decent discount.
However, those deals are all about context. I live on my own, I'm a cheapskate, and -- most tellingly -- I don't own a car. So there's no reason for me to opt in to this particular deal.
That's a really obvious point, but many people are immediately tempted to spend money for its own sake just to take advantage of what looks like an individual deal. While the offer you get might be tied to your loyalty card number, you can be sure that you are not the only person getting that offer. And the only criteria to judge these offers by is: will they really save you money? If so, go for it. If I had a vehicle, this would be something of a no-brainer -- I'd fill my pantry and fill my car. But I'd think about it first. Make sure you do too.