In the last week we received ~470000 crash reports, these do not represent all crashes because it's an opt-in system, the real number of crashes will be several times larger. Still, out of these ~2500...
In other words up to 10% of all the crashes Firefox users see are not software bugs, they're caused by hardware defects! If I subtract crashes that are caused by resource exhaustion (such as out-of-memory crashes) this number goes up to around 15%. This is a bit skewed because users with flaky hardware will crash more often than users with functioning machines, but even then this dwarfs all the previous estimates I saw regarding this problem. 3/5
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