Some search engines have, in the past, had problems with dynamic pages, that is, pages that use a query string. This was not due to any technical limitation, but rather, because search engines knew that it was possible to create a set of an infinite amount of dynamic pages, or they could create an endless loop. In either case, the search engines did not want their crawlers to be caught spidering endless numbers of dynamically generated pages.
Google is a newer search engine, and has never had a problem with query strings. However, some dynamic pages can still throw Google for a loop, and to avoid that Google may limit the number of query string'd pages it crawls from any individual site.
Some shopping carts or forums store session information in the URL when cookies are unable to be written. This effectively kills search engines like Google because search engines key their indexes with URLs, and when you put session information in the URL, that URL will change constantly. This is especially true as Google uses multiple IP addresses to crawl the Web, so each crawler will see a different URL on your site, which basically results in those pages not being listed. It is important that if you use such software, you amend it so that if cookies are unable to be written, the software simply does not track session information.
So, you don't need to use search engine-friendly URLs to be listed in Google. However, these URLs do have other benefits, such as hiding what server side technology you use (so that you may change it seamlessly later), and they are more people-friendly. It is still a good idea to use search engine-friendly URLs if you can.
This is a relatively minor myth but it still pops up (pun intended) every once in a while. Google has an advertising program called Adwords, and one of their policies is that they do not allow sites that use popup windows to participate in this program.
Google has policies against the use of artificial means to increase your PageRank, which specifically include things like joining a link farm. There are sites or services out there that set up automatic link exchanges to increase your PageRank. The links are usually hidden from people through the use of CSS, and either making the text the same color as the background, or by putting the links in an invisible layer. As search engines don't render CSS, they will see the hidden links and thus count them when calculating your link popularity.
However, despite all this, Google will not penalize you for being linked to by a link farm. After all, you have no control over which sites links to you, so it wouldn't be fair to penalize site owners on this basis. Additionally, link farms often have low PageRanks and a high number of outgoing links, so each link will contribute only a very small amount to your total PageRank -- and thus this method of abuse is not very effective.
Even so, Google can punish you if you link to a linkfarm from your site, or otherwise put hidden links in your pages. So the simple truth is that you can be punished for what you do to your own site, but not for getting linked by another site.