With the rise of cheap DNA testing sites like 23andme have opened a Pandora's box on the practice of sperm donation and is blowing apart any previous notions of donor anonymity.
This article discusses this in good depth and gives real life examples of the results of this and the challenges and emotions faced by all parties.
Considering that only a small percentage of a population needs to tested to allow familial links and relationships to be uncovered these cases of de-anonymisation are likely to rise.
There are numerous other ethical factors to consider with the rise of this technology such as the revealing of life limiting diseases such as Huntington disease and of course will health insurers and prospective employers eventually ask people to submit to these or simply scan the data base to make familial links. Will children's education be based on their genetic makeup. The article doesn't cover all these issues but it is fascinating look at the sperm donor industry and home DNA testings effects in it.
"Years passed, and on August 12, 2015, Colin awoke to a startling message. “It’s come to my attention that you’re my biological son,” it said. Colin figured he was experiencing some DNA kit version of the Nigerian prince scam. When he navigated to 23andMe’s DNA Relatives tab, an unfamiliar name topped the list: Jeff Johnson. “50% shared DNA,” the screen read. Under “Relationship,” it said, “Father.” Maybe that message wasn’t a scam after all."