People here love masks, and not only during porcine pandemics. You see the masks everywhere during flu season and in spring, when pollen counts are high. They do keep out a lot of pollen, and they stop your coughs and sneezes from bothering others. As a side effect, a mask prevents you from touching your face, a common way to catch infections and the reason we're advised to wash our hands during flu and cold season.
But the kind of cheap disposable mask the gentleman above is wearing can't really protect you from a virus; it's really little more than a piece of conveniently shaped tissue after all. A real surgical face mask can protect you against bacteria and it has a minor effect against a virus; for reliable protection, however, you need a mask rated for virus protection (the ratings name differ by country; it's called things like P2 or N95). [Note: I'm no physician, so don't take any of this as the plain truth; read footnote #1 below2.]
Using real masks is not really an option for most people. First, to use an antiviral mask properly you need to know what you're doing: how to put it on so it fits you tightly and correctly; how long to use it before it needs to be replaced; how to take it off without accidentally touching virus-laden surfaces and getting infected; how to dispose of it so it doesn't infect someone else. Do you know how? I certainly don't3. Also, virus-protective masks are pretty expensive and somewhat uncomfortable.
The reality is that most people will wear the mask wrong, will start to use it but soon give up, or use the mask only when they're seen by other people. I sometimes see people wearing paper masks with the nose uncovered, for instance, completely defeating any protection. Or taking it off when talking on the phone, as if the virus would be polite enough to wait until the call is over before it tries to infect you. Overall, even a real mask would be largely (though not completely) ineffective as a large-scale protection measure.
So while there's a minor benefit to wearing a mask, it seems the typical official recommendation is that you use an antiviral mask if you're in close contact with a sick person (if you're nursing a family member for instance), learn how to use it properly and make sure you really do use it all the time. If you are out and about, there is no reason to bother with a mask as the benefit is very minor.
Are masks - cheap unrated masks especially - completely pointless? No, not at all. There's several reasons to use a mask and avoiding infection is only one of them. A cheap mask won't prevent you from becoming infected but it does protect other people from you. As you breathe, cough and sneeze, the water droplets in the air mostly stay in the mask rather than spreading far and wide. And as we saw earlier the mask prevents you from touching your face. If you aren't diligent about hand-washing this can help stop you from infecting yourself.
But the most important thing about the mask is, I think, that it's a security blanket. People may know or suspect that it's nearly useless in practice, but it gives them a way to do something constructive about a scary, confusing situation they have no control over. It lets people control their fear, and it gives them the confidence to go outside and conduct their daily lives without being paralyzed by fear and uncertainty. The mask is also a signal to others. It shows them that you're mindful of the situation, careful and conscientious. You're wearing a mask so you're probably doing all those other protective measures you're supposed to and thus you're safe to be around. Masks may not slow or stop the spread of virus, in other words, but they may well slow or stop the spread of unfounded panic. And that may in the end be more important than the virus itself.
#1 Note those "seems" and "I think" in the text: I'm not a medical professional of any kind. I've never studied medicine and I have no more or better information than the average twelve-year old. I have no idea what I'm talking about. This post does not constitute medical advice. Do not depend on information here for any medical decisions. This post may contain information that is outdated, misrepresented or outright wrong. Do not read this and drive at the same time. Keep out of direct sunlight. If a rash, lower back pain, headache or a serious case of death occurs during reading, please consult your physician. Do not mix with isopropanol. Do not eat. Do not cover. Duck and cover. The satanic messages you think you hear when you read the text aloud backwards are just an illusion. Lift with your knees, not with your back. The backstroke is possibly the most scenic of swim styles. You have to be this tall. Void when wet.
#2 It's the one right above.