Is male infertility a common problem?

Yes. It is estimated that of all couples who experience infertility, 40% are male factor problems, and in another 20% there are problems with both partners. It's not as dire as it may sound though: male 'infertility' doesn't usually mean the couple can't have a child, just that they may need some help.
Here are some ... Largely, some 15% of couple may have difficulty to conceive within one year of nonprotected sexual intercourse. Among them, females are responsible some 50% of cases; males, 30%; female and male, 20%. In men, most common cause is still idiopathic (unclear) although varicocele is the most common identifiable cause for possible male infertility in 35-40% of men as compared to 15-20% in general popul.
Yes, very common. In couples trying to conceive there is a sperm issue about 40-50% of the time, ranging from mild to severe sperm problems. Semen analysis is an important part of infertility testing. Sometimes the sperm issue is the only problem we find when we test both partners, often there are male and female factors together. Even if the man's sperm is 'normal' it helps a lot if the male partner is supportive.