PageRank is based soley on the incoming links to the page, there are no terms in the equation that mention outbound links,except that the amount of
PR passed is divided equally among each outbound link on the page.
Google suggests that you do not have more than 100 links on a page, but I have seen pages with 500 or more links indexed. When you get more that 100 links on a page however the spidering and indexing of the pages linked to can be slow, however.
Its not the number of links that makes it a link farm, what if your menu system has 100 links, would that make every page in your site a link farm?