you really shouldn't add or accept random people as, not saying they all are, they may be perverts, hackers, 'trollers', bullies or fake accounts. I know it doesn't seem to bad as you can block people but by accepting your also putting your friends and family in danger as they could add them to and get their information or harass them and no one likes some 60 year old chatting up their nearest and dearest (just an example) but still, I always ask people why they added me if I don't know them and if we gave mutual friends, I ask the mutual friends about them and if they don't know them in real life I don't accept as you never know about people online. plus it is a hacker then they can get your email details, hack your account and get your friends or get bank details and who wants to pay off someones debt or have your good credit ruined for a silly friend request.
sorry about rabbiting on haha (:! hope I helped!(: