SUMMARY: It's an agonizing decision. You slaved over the latest issue of your email newsletter, and yet, only perhaps 30% of recipients opened the darn thing. Should you resend to the 70% who didn't?

On one hand these are permissioned names who said at sign-up that they really want your newsletter.

On the other hand if you annoy anyone, it could damage your reputation and there goes the brand (let alone delivery past filters).

Here's a new MarketingSherpa Case Study about a UK marketer who undertook this slightly dangerous test this fall. Includes samples and lots of useful data:
http://www.marketingsherpa.com/sample.cfm?contentID=3139
(Open access until Dec 18th)