First and foremost, cyclists need to follow traffic laws. If that means they need to approach stop signs just like drivers do -- stopping completely before proceeding -- then that's the law they should follow.
However, you have probably seen cyclists roll through stop signs at times. They slow down, coast, look both ways, and then keep on riding. Why do they do this?
The reason is energy. A driver can stop a car and then start again without expending any more physical energy than it takes to press down on the gas pedal. A cyclist, meanwhile, can maintain a bike in motion with little expended energy, but he or she has to use a lot more to start it up from a stop. In short, stopping a car doesn't really change the driving experience, but it does change the cycling experience.
Of course, that doesn't mean riders never stop. They mainly just do this when they don't have any opposing traffic to contend with. They know that they don't have the right of way if other cars are driving through on the cross street, so they stop and wait. If there's no traffic coming, though, they often do not feel like it makes sense to completely stop. A bike rolling at five miles per hour is virtually stopped anyway, and the rider can still make sure the way is clear.
Unfortunately, this sometimes makes drivers angry, and they may drive aggressively around cyclists as a result. That can lead to accidents. Those who get hurt need to know their legal rights to compensation.