This past week I encountered two otherwise interesting and compelling stories, one by email from a friend and the other a story shared by a Facebook Friend. I say otherwise as they both turned out to be false, fake, urban legends or a story that was embellished.
Now there's nothing illeagl about passing along these stories via email or sharing them on Facebook but, knowing what I do, I am compelled to check the accuracy of such a story before passing it along to others, or commenting on it.
And while it's not illegal, if you forward one of the 'chain' emails it could contain mal-ware (virus, trojan horse, etc - that is designed to infect the recipient computer) or it could also be the harvesting work for or of a spam-bot...that will get your valid, live email address for all their spam campaigns.
Here is some additional good info on the topic of sharing or spreading hoax stories and emails Toxic Excuses on About.com.