Surely all contact tracing methods have false positives and false negatives. Do they all have "no value"?
Technologists have a duty to explain the limitations of the technology, but I don't think they should be drawing conclusions and making public health recommendations.
Let's assume someone got bankrupted by a hospital over a severe coronavirus case. This means that someone has been wandering around for weeks infecting others. Let's assume there is a chain of 10 contacts between me and that someone. The probability of virus transmission is 1% (and I'm generous here) because more people wear masks, because people avoid talking and generally avoid interactions. Probability of transmission over 10 links is 10^-20 and we may stop right here, unless we plan to study quantum particles.
Now let's assume I get a notification that I might have been infected over the past few weeks. The probability that the app is correct is abysmally low. But even if I get infected, I'm unlikely to get sick and I'm unlikely to transmit the virus to others because masks, social distancing and because I already assume I'm infected.
So yeah, this app would be useless and is only good for surveillance.
(But I'm very uneasy about these app-based approaches, and much more in favor of hiring tons of humans to do contact tracing instead, or at least as the primary mechanism.)
"you've come in contact with someone infected! use this coupon code to get 10% off your test at select locations. Need a mask? click here to buy one and save your family".
If that were truly the case why are there still transmissions? Wouldn't that imply that in a matter of 5 months it will be impossible to get the disease strictly due to the timeline and required links? ~14 days of transmissible * 10 transmission events / 30 days in a month = 140 days before no more mathematically possible transmissions. Wouldn't that require us being repeatedly exposed to every person on the planet to keep those numbers to a possible level?