Open-source contact tracing, part 1

You're not actually handing out your contact information with the good scheme. You're giving out a random number that you could use to tell anyone who got it that you want them to know one particular thing, and you pick a different one every 15 minutes. It's a random phone number that only makes outgoing calls, and I give it out so that people who get it know to pick up and get the message. Furthermore, I can't call anyone in particular (even if I got a number from them), I can only call the entire population of the country, and they block calls from every number they don't recognize.

In particular, unless I choose to reveal my secret key: (a) nobody can contact me at all without me going looking for messages for me; (b) nobody can tell I'm the same person an hour later. Even if I reveal my secret key, nobody can tell who my contacts are, aside from each of my contacts being able to tell that they're one of them, and even they can't tell it was me unless they remember (and knew) who they were around at that time.

As far as whether it's beneficial: I haven't gotten tested at all, like 90% of the people in my state. I'm 99% sure that I haven't gotten infected more than 2 weeks ago, since I've got a bunch of housemates, and none of us have have symptoms. There's unused capacity to test more people here, but we can't test everybody at once (for social distancing reasons, if nothing else). It would be useful if the system told 5000 people a day to get tested, even if only 5% of those tests came back positive, since we could easily test 5000 more people every day and our current positive rate is only 1.9%. It would be a somewhat more useful application of 5000 tests than each person randomly deciding to get tested one out of every 2000 days, even if our masks were 95% effective at making our contacts safe.