Google’s recommendation is to keep the links on a given page to a reasonable number (fewer than 100). It’s because, Google used to index only about 100 kilobytes of a page. If a page started to have more than that many links, there was a chance that the page would be so long that Google would truncate the page and wouldn’t index the entire page. At any rate, you’re dividing the PageRank of that page between hundreds of links, so each link is only going to pass along a minuscule amount of PageRank anyway, said Matt Cutts.

Here’s an interesting chart by Nick Bilton of NYT that visualizes the number of links on the homepages of popular websites.