It's about the large number of children sperm donors in the US are fathering because of the lack of regulation of sperm donation clinics (unlike the US). The article is mainly concerned with the fact that the fathers did not know about the large numbers of children they would be having, and the fact that the children of the sperm donors could have a lot of other half siblings, unbeknownst to them, and risk incestuous relationships.
It did touch on the fact that rare genetic diseases could then be more prevalent in the population because of this preponderance of offspring of a few individuals that could be carriers for a disease. But it also got me thinking, could you even consider this a sort of unnatural population drift? Maybe drift isn't the correct term, but it does seem like a overrepresentation in the gene pool of a few individuals. This has obviously happened before, bringing to mind the famous example of Ghengis Khan. But here we have a different situation where men who are not "actively" involved are fathering a ton of offspring. These men might not have been viable mates outside of the sperm clinic context for any number of reasons as well (or maybe they would be more likely to have many children ...I don't know anything about sociological aspects of sperm donors but I'm sure there's a study out there somewhere).