How should one proceed when they receive no job offers after a considerable amount of applications? I'm getting way ahead of myself, but being nervous on the job market I asked an advisor what happens should a candidate receive zero job offers. To which the reply was, "That never happens."

I'm sure that some people have had this experience before. I'm in the social sciences in a discipline that is very competitive with fewer than normal options outside of academia. I still have a ways to go time wise for job expectations, but I am curious about what options others may have gone for in situations where they either received no offers or none that were more appealing than something else that wasn't planned.

My assumption is that people will shoot for adjunct positions or similar options should nothing else come along, and try again in following years. Can anyone speak to being in this kind of position, or knowing someone who has gone through it? 

Of course I expect and hope not to be in this position, but I am planning for everything. Others have told me that they apply for upwards of 70 positions in a year, which to me is insane (I don't know how assured I could be in the quality of that many applications). I have probably applied for 20-25 positions thus far, so I don't know if I should be approaching the process differently. And in the worst case situation, where to go from there? 

Edit: Thanks all for your sensitive and helpful comments.
It certainly does happen. And when it does happen, people tend to leave academia for a job in industry, commercial sector, retail, etc.

Unfortunately, the current culture of academia still tends to focus on success stories and turns a blind eye to unlucky candidates, almost treating them as they never existed. Your supervisor's response falls is this sad mainstream paradigm.