When I signed up for 23andme many years ago, it was via a friend in another country, who re-mailed it for me under a fake name and paid in cash. For some time I would log in through a locale-specific 23andme sub-domain until they eventually merged it all together.
It wasn't long before they figured out who I was and placed me within my family tree. My fake name now lives among near and distant relatives I was not aware had signed up themselves or their parents/grandparents. They know who I am, who my siblings and cousins and aunts and uncles are, etc. This was always going to happen as soon as I sent them my sample.
I never believed my anonymity trick would truly work, I just wanted to make it sufficiently difficult for when 23andme inevitably sold out, got gobbled up, or turned evil. I learned what I wanted from the service, and have only logged in once a year or so since to see if they updated any findings or disease studies.
While I truly appreciate the concept of bringing privacy and anonymity to this field, it's worth considering we are all quite easy to identify using these samples.