According to eMarketer, email marketing is still a very effective means of driving e-commerce. The following is an excerpt from eMarketer's article, "E-Mail Marketing Still Works"...
First, the good news: permission-based e-mail is great at getting consumers to buy.
Half of US adult e-mail users surveyed in April 2008 for Merkle's "View from the Inbox" study, conducted with Harris Interactive, said they had made an online purchase in the previous year as a result of permission-based marketing.
In addition, e-mail was second only to customer reviews on Web sites for influencing online purchases, according to DoubleClick Performics' "Green Marketing Study," conducted by Opinion Research Corporation in February 2008. E-mail was roughly equal to search results in terms of influencing online purchases.
SPAM emails are obviously a huge problem, but when consumers expect to receive an email from a merchant, they obviously open those emails and respond in a material manner. Our experience suggests that email marketing is here to stay and in fact, is going to grow in importance for online merchants because there are few, if any, more cost effective ways to drive a sale than to market to your current and past customers via email. Having said that, consumers are increasingly likely to stop doing business with a retailer if the retailer uses poor email practices. Therefore, there is a huge opportunity here for merchants, but if done incorrectly, it can be costly.
Make sure you understand email best practices. EmailLabs has produced nice list of email best practices that might be helpful for you.
Once you have acquired your customers via more expensive channels like Paid Search Advertising, eBay, or CSEs, make sure you keep them buying from you on a consistent basis by offering them interesting offers via email. This really is a no brainer.
Read more of the eMarketer article here >> E-Mail Marketing Still Works - eMarketer