Morph
When you've worked as long and hard as I have to fight for affiliate marketing per se as an industry then you may have a right to challenge my business acumen - many on here will know my business acumen is good and sound, so don't challenge me on that one sunshine as there will only be one winner and it won't be you.
I'm not sitting here with a broad smile on my face - equally if you reckon discount codes have such an easy time of it, why don't you create one (and please don't say 'my ethics wouldn't allow it') or I really will want to order you a string quartet.
"There's no begrudge about it. I simply wouldn't pay the affiliates where 90% of their traffic stream comes from visitors typing in "brand + voucher"." - so by your business acumen it's fine to defraud your affiliates then by not paying out on valid commissions (by my book if it doesn't breach network or merchant terms and conditions it's a valid commission) - or do you have that in your merchant terms and conditions and lose a good percentage of affiliates promoting your programme?
"Many merchants do not have valid codes. Even the ones that are stated as "valid" do not in fact work. The merchant hasn't put an expiry date on" - so how is that the affiliates fault exactly?
"Click the link on the code site, and on 95% + of occasions, nothing?" - what if there is a code though, do you use it - and do you still delete the cookie in which case YOU are stealing the discount site's commission are you not (or is that bit of business acumen ok with you?)
Voucher sites are most definitely not an easy leeching business model, a properly maintained voucher site takes many man hours to maintain.
"Most people decide what to buy, then look for the store to buy it at, THEN when they're at checkout, decide to go looking for a code" - I'm not disagreeing with you, it doesn't mean though that if they find a code for your competitor at that point they won't go off and buy from them instead...
And for the record - I don't have any 'dodgy' voucher code practices, I don't hide the voucher codes at all - people can click or not click it's up to them (though fortunately a good number do

) - so I'm not defending my personal interests, my voucher code contributes less than 10% of my income - but equally I'm not prepared to see an unwarranted witch hunt by someone whose only contribution to the forum thus far has been to attack other people's business model without sharing anything of their own business model - just what exactly are you so afraid of?