First of all its not linkbatting its Linkbait, and is essentially a piece of content placed on a web page, whereas farming is just building links of your web site on world wide web which google counts and helps in PR(some may agree to it and some may not)
Link bait :- Matt Cutts defines link bait as anything "interesting enough to catch people's attention." and link farm :- On the World Wide Web, a link farm is any group of web sites that all hyperlink to every other site in the group. Although some link farms can be created by hand, most are created through automated programs and services. A link farm is a form of spamming the index of a search engine (sometimes called spamdexing or spamexing). according to wikipedia.org
The process of exchanging reciprocal links with Web sites in order to increase search engine optimization. The idea behind link farming is to increase the number of sites that link to yours because search engines such as Google rank sites according to, among other things, the quality and quantity of sites that link to yours.A link farm is a Web page that is nothing more than a page of links to other sites.