A short year or two ago, many people considered it unwise for a rowdy young person to have a Facebook account under his or her real name. Now, many potential employers and psychologists — even potential paramours — consider you "suspicious" if they can't find you on the ubiquitous social network. Is it worrisome if someone doesn't have a Facebook account? Here, a brief guide:

Who says you have to be on Facebook?
Everyone from human resources managers to mental health experts. One psychologist told the German magazine Der Taggspiegel that having a Facebook profile — under your legal name — is a sign that you have a healthy network of friends, colleagues, and relatives. The flip side, says Britain's Daily Mail, is that being on Facebook is now so indisputably normal that those who lack a public profile are viewed as, well, abnormal.

What could Facebook invisibility suggest?
It could be "the first sign you are a mass murderer." At least, that's how a post on Slashdot summed up the Der Taggspiegel article, which pointed out that neither suspected Aurora theater gunman James Holmes nor Norwegian massacre shooter Anders Behring Breivik were on Facebook (Holmes was on Adult Friend Finder, and Breivik on Myspace). Suggesting that more than a few odd Facebook abstainers are dangerous sociopaths is obviously "a tad extreme," says Kashmir Hill at Forbes, "but I'm seeing the suggestion more and more often that a missing Facebook account raises red flags."

Such as?
An increasing number of human resources departments are starting to wonder whether job applicants they can't find on Facebook are hiding something. Too many photos of drunken carousing — and other damning evidence — to use your real name, maybe? Also, if your new love interest is invisible online, is that because he's really married, or otherwise not who he says he is? "If you are going out with someone and they don’t have a Facebook profile," says Farhad Manjoo at Slate, "you should be suspicious."

Is that really fair?
"I, personally, am suspicious when I meet someone" who isn't on Facebook, says Katie J.M. Baker at Jezebel. It doesn't mean they're bad — just a wannabe member of the counterculture who's going to subject me to "a pretentious rant about how he doesn't even own a smartphone, either." Fair or not, the reality is that 90 percent of recruiters glance at job applicants' Facebook profiles, says Zoe Fox at Mashable, and some will assume people they can't find are hiding offensive stuff that would make them look bad. Bottom line: "There are more than 955 million Facebook users, and it could hurt you to not be one of them."

Sources: Daily Mail, Forbes, Jezebel, Mashable, Slashdot, Slate