[edit]

Looks like the calculation was revised [0] after criticism:

> Under these assumptions, you'll have to wait about 33 to 600 days to get a 96% chance of getting a bit error.

What's more worrying is the variance, the above calculation is based on expected well behaved DRAM.. yet some computers just seem to have manufacturing defects that make the incidence of errors high enough to be a regular problem.

[0] http://lambda-diode.com/opinion/ecc-memory-2