Online classifieds site Craigslist is so effective that, according to a ClickZ article, commercial marketers are breaking the rules to pitch their wares.

Craigslist warns users that commercial posts are subject to removal if placed in sections other than the "services offered" area. Its terms of use require that users not post content "that constitutes or contains 'affiliate marketing,'…that constitutes or contains any form of advertising or solicitation if: posted in areas of the craigslist sites which are not designated for such purposes…[or] that includes links to commercial services or web sites, except as allowed in 'services.'"

Yet, according to ClickZ, readily available automated Craigslist ad posting software, a book dedicated to marketing goods and services through Craigslist and a syndicated article providing guidance on marketing via free classifieds on the site that has been making the rounds on various business-oriented websites lately, all tempt marketers into adding the site to their mix. And create controversy within the industry.

To find out why local classified marketing is so hot, read Mark Naples' interview with Craiglist founder Craig Newmark.