It depends. I recall one project with flaky tests, and shortly after joining I decided to investigate. It turned out to be a problem with floating-point values

It depends. I recall one project with flaky tests, and shortly after joining I decided to investigate. It turned out to be a problem with floating-point values in the shopping cart logic. Tests were using random item prices, so sometimes it appeared and sometimes not. I'm glad I found that one. :-) On the other hand I've seen something like @flaky used in the Ruby world to run Capybara tests with a lot of Ajax, where you get failures because of timing issues deep down inside Selenium. It's not a problem with production or your app, but your testing tools. In the second case I still am not totally comfortable, since it makes it easier to overlook flaky tests that really do need attention, but I can understand it there.