Entrepreneur Daily posts on a survey on consumer attitudes towards traditional mail and email. Conducted by ICR and sponsored by Pitney Bowes, the majority of survey respondents preferred to receive marketing communications through the traditional mail. Key quotes from the blog post:
"73 percent of respondents prefer to receive new product announcements and offers from companies they do business with by mail."
"70 percent prefer receiving unsolicited product and services promotional info by mail."
Traditional mail clearly can still be effective. This is particularly true if the targeted consumers don't have Internet access or don't actively use the Internet - and a lot of Americans fall into these categories. Pew/Internet has a study that segments Americans by technology use. Key quote from the study summary:
"49% of Americans only occasionally use modern gadgetry and many others bristle at electronic connectivity"

