Why Use Email Marketing?

I recently attended a workshop hosted by Constant Contact about the best practices of email marketing. With so many spammers, many wonder if they should use email marketing. Once you put into practice the 'best practices' of email marketing, it can be a very fast, easy, inexpensive and effective way to market. Some statistics about email (source: AOL Email Survey - July 2008) are:

46% of email users say they're "hooked" (addicted to email)
51% check email 4 or more times a day
69% of email users say they have multiple email accounts
62% check work email over a typical weekend
50% check email while on vacation

So people still turn to email to find valuable information. There are reasons to use email marketing? How can it be used most effectively? That's another discussion.