Here are 2 more bad SEO Tactics:

1. Cloaking
Cloaking is a search engine optimization technique in which the content presented to the search engine spider is different from that presented to the users; this is done by either looking at the IP addresses of who is requesting the page, or by looking at the User-Agent HTTP header. While there are some legitimate uses for cloaking, like giving text to the search engines while giving Macromedia Flash to users (since search engines can't understand Flash), cloaking is most often used to try to trick the search engine into giving it a higher ranking than it would get without cloaking; it can also be used to trick search engine users into visiting a site that they ordinarily wouldn't, because the search engine's description of the site differs from the site's actual contents. For this reason, sites that are discovered to be using cloaking are permanently banned by most search engines.
Cloaking is a form of doorway pages technique.

2. Link farm
On the World Wide Web, a link farm is a large group of web pages created that contain hyperlinks to one another or a specific other page. Link farms are normally created by programs, rather than by human beings.
The main purpose of a link farm is to deceive the indexing programs of Internet search engines that assign rankings according to the number of pages that link to a specific page. If the link farm works as planned, the search engine will believe that the promoted page is hugely popular because of all the pages that link to it and give it a high ranking. Search engine operators consider link farms an abuse and attempt to detect them, to remove them from their indices or penalize their content rank. Free For All link pages are a particular type of link farm.

This article has been made using some sources: wikipedia