There are a few things in place that will make that scenario extremely rare.
For one, when you hear about the type of crazy stories where a donor contributed to hundreds of kids, it’s most likely referring to a rogue sperm donor, not an egg donor. Egg donation is truly different in kind. Per ASRM, the governing body of reproductive medicine, the recommendation is for a donor to be able to donate up to 6 times. In addition, unlike sperm where one donation can yield in millions of sperm, in an egg donation cycle, about 18 eggs result, of which only a smaller percentage can result in an embryo. A donor is also prohibited to donate if more than 25 kids result from donations- to note, we have never gotten near that amount and have never had to cut a donor off because she has produced too many donor babies.
Secondly, we are an egg bank that works with recipients from across the world and donors from across the United States. This is in contrast to an IVF clinic with a donor program, where donors are recruited locally and where recipients are also all local. In working with an egg bank like ours, therefore, the probability of two recipients choosing the same donor within the same vicinity are much, much smaller – and therefore the type of scenario of donor-conceived kids dating each other is very unlikely.
Thirdly, but not last, the conversation is changing these days. More and more egg donor recipients are having the discussions with their kids about their origin. This leads to less likelihood that a donor-conceived child will be unaware that she/he is dating another donor-conceived child, since they’ll be more wary and aware of themselves and of others.