It seems that as the recession has pushed retailers toward focusing on results, those retailers have looked more and more toward direct-marketing and retention. And the direct-marketing darling of the online marketing world is email marketing. As AdAge reports:

E-mail has emerged as a recession darling, as retailers look to proven programs that are cost-effective and results-oriented. That's led to increasing investment in technologies that better target customers and serve up more enticing messages.
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Thanks to its cost-effectiveness and retailers' recession-era emphasis on retention -- Shop.org says that the number of companies focused on retention has nearly doubled in the past year [...]

Many affiliates are focusing on offering consumers increased saving these days. So if you're promoting deals that have an expiration date, email is a great way to reach those users who might not visit your site before that deal expires.

Indeed, email marketing is a great retention strategy because it reminds consumers that you still exist. So this makes it a great time for affiliates to start looking at how to better leverage their email lists. And if they don't have an email list, it's a great time to consider how they can start collecting targeted and qualified email addresses.