Welcome to the Q&A Forum

Tons of sitewide links all at once can hurt a site that has very few incoming links, they get discounted anyway so the best thing to do is to get a homepage link only since the homepage is usually the highest PR page on a site, and well crawled by Google. Also, being linked to from a penalized or bad neighborhood can hurt you so you should vet your incoming links and remove any offending ones. Too many links at once I do not believe is a factor, because Google is not going to penalized a site just because it goes viral, it is more about the TYPES of links and diversification of those links that can trigger a penalty.