One ADVANTAGE of non-random sampling is that you can choose the sampling to reflect the results you WANT to obtain. If I want to make a hypothesis and prove it, I only sample the specimens that support my hypothesis.
One DISADVANTAGE of true random sampling is that it may not be helpful in finding an answer to the problem. If I want to find a cure to cancer, it is much more helpful (and efficient) to sample people who HAVE cancer. Of course you still need to sample people without cancer to see differences.
One DISADVANTAGE of true random sampling is that it may not be helpful in finding an answer to the problem. If I want to find a cure to cancer, it is much more helpful (and efficient) to sample people who HAVE cancer. Of course you still need to sample people without cancer to see differences.