No need to apologize even if you did do it yourself. I checked your previous submissions and it is obvious you are not spamming HN. There is no shame in linking to a interesting product using an affiliate program. You are technically advertising for them after all and deserve a payment.

I do wonder how much you earned the Stumbleupon user though. A quick google search on the affiliate suffix shows he links to a few other DX products on SU and elsewhere. Today I'm sure he saw a boost in profits.