From Forrester's Press Release

Spending on email marketing in the US will balloon to $2 billion by 2014 — a nearly 11 percent compound annual growth rate — according to a new forecast by Forrester Research Inc. (Nasdaq: FORR). Falling CPMs (cost per thousands), a high return on investment, and growing consumer use of social email accounts will fuel the use of email by Direct Marketing professionals. In five years, consumers will be deluged with more than 9,000 email marketing messages annually.

“By 2014 direct marketers will waste $144 million on emails that never reach their primary target,” said Forrester Research Vice President and Principal Analyst David Daniels. “Successful Direct Marketing pros will alter their tactics to overcome inbox clutter and increase relevancy.”

My view:
Email in marketing should only be utilized as it relates to a promotion, major announcement or a giveaway. Please don't contact a potential buyer just to tell them your company exists or let them know you are thinking about them. Give the buyer something valuable in the email that might improve their day. These are good habits.

Although I think email is a good and measurable way to accomplish direct marketing, I also think we need better tools to filter the types of organizations sending email. Sometimes the best defense is to keep changing your email address similar to a witness protection program. Congratulations to the email provides such as Exact Target or Constant Contact since it appears growth will come easily and their challenges will be more long term strategy than short term revenue.