Today I read an article in eMarketer:

In early Q4 2004, the e-tailing group signed up with 100 retail companies to receive e-mail marketing. The e-commerce consulting firm found that 65 of these 100 merchants sent e-mails between November 22 and November 26, 2004, the period right before Thanksgiving. Read more...

I am an big fan of email as long as it is done well. Businesses I feel have to be careful when doing email promotions. They want to make sure that they are not perceived as spam and they d\shouldn't bombard their customers with emails either. Plus good common practices such as emailing only those who have opted in (permission based) should be emailed, they should have a clear way to unsubscribe and really, the message should be pertinent and enticing to your custome, otherwise they won't want to read any future emails you send them.

At any rate, read the article. It provides some info on types of emails that consumers (in the US) consider to be spam.