Internet Retailer reports that some 33 percent of U.S. consumers, compared with approximately 20 percent worldwide, shop less online because of spam and internet-based fraud, according to a new poll from market researcher GMIPoll, which surveyed 20,000 online consumers worldwide. And 57 percent of those polled blamed the marketing and advertising industries for the increase in email. ISPs came in a close second in most countries.

Approximately 65 percent surveyed worldwide said they are receiving more spam than a year ago: 29.5 percent received spam of a sexual nature, and 22.5 percent received financial spam, which was the number one type in the U.S., China, Russia, India, Denmark and Poland.

The survey also found that anti-spam software is most popular in the U.S., where 43 percent of those polled had installed it. Yet, 53.5 percent of Americans said they still choose to delete spam manually, and 69 percent worldwide said they now open email only from people they know.