Nobody knows exactly how many children are conceived with donated sperm, but an estimated 30,000 to 60,000 such babies are born in the U.S. each year. According to The New York Times, many of these children have more half-siblings than their parents bargained for. One mother, Cynthia Daily, used a donor registry to trace at least 150 children to the same sperm donor who fathered her son. "It's wild when we see them all together — they all look alike," says Daily, who sometimes vacations with other families who used the same donor. But such large pools of related offspring face increased risk for rare genetic disorders, not to mention accidental incest between donor siblings. Is it too dangerous to let one man father 150 kids?

Yes, we need an intervention: It's nice that so many infertile couples are having kids with the help of sperm donors, but the U.S. donor-bank industry needs to be regulated, as in other countries, says Sam Biddle in Gizmodo. Granted, "a government eye on the conception of children" is a little spooky, but I'd rather err on the "sci-fi dystopian" side than deal with gene mutations and the "gross factor of half siblings having sex on a large scale."
"Overused sperm means bigger risk of brother/sister sexin'"

Don't interfere in this Darwinian unnatural selection: Clearly, this "dude with 150 kids" is doing something right if "150 different women independently chose his DNA as 'the right stuff,'" says Matthew Kahn in Environmental and Urban Economics. Sure, we need a diversified gene pool, but if all these ladies looked at the menu and chose "this guy as the King," perhaps we should be paying him more for his high-quality DNA instead of stopping him from producing.
"Selfish reasons to have more kids?"

What about the kids? Without government regulation, parents have created networks to "work through the thorny issues" of having so many half-siblings, says Cathy Ruse in National Review. For example, "one mother has instructed her child to memorize the donor number of her father so that she can compare notes with possible future mates." Which raises the biggest question: How much damage does having 150 siblings inflict on "the tender psyche of a little child"?
"Brave New World: Sperm donor daddy tracks 70 children on Excel sheet