If I had a nickel for every time I read somewhere that having more than 100 links on any page would send up flags in Google, I might be able to pay off my mortgage by now...
While I believe there is some truth to this, as in, if you have a FFA (Free For All) site, or a link farm where anyone can add links, then I could see where this would be detrimental to your rankings.
However, if you have relevant links on your page pointing to other sites similarly themed to your site, how can you be penalized? Who's Google to say how many relevant sites there are about your topic?
How could Google (or any other search engine for that matter) tell us, web users, who their friends are?
Suppose I have a website about NFL. Maybe I have a page that has every player listed, and a link to their stats - currently, that would be around 500 links. All those links would be relevant, and all links are pointing to unique content. How could any search engine surmise and penalize this?
The Internet is growing at such a rate that it's very conceivable that search engines will never be able to index every piece of virtual real estate web has to offer. And with growth, comes more places to be found, and in return, more places to link to.