Exhibit A: eBay
According to the email (in which the most commonly repeated phrase is my username), I could win an iPad or a $500 AMEX card.
But, if you've already got an iPad,don't bother.
Exhibit B: American Express
American Express wants your opinion. A nicely done, simple email asks you to complete a survey.
I imagine a lot of people clicked on the email but then bailed here.
If you already know who I am, and you're not asking me to access my account or pay my bill, why make me go to the trouble of signing in? It's just a survey. "Fast and Easy" isn't sufficient motivation.
I regularly complete surveys for e-Rewards, but I also get a lot of email. If it's going to take extra work, or waiting until I get back to my laptop, the bar's gotta be pretty high. Neither of these clear it.
In both cases, I deleted the emails and moved on.