Thanks to the research done by Bianca Schroeder, Eduardo Pinheiro and Wolf-Dietrich Weber about errors that occur in DRAM memory, now we know that it is possible a single machine to have 48621 errors (correctable errors) per year. Roughly this makes 133.20 (48621 / 365) errors per day or 5.55 errors per hour.
The research is based on DRAM memory equipped with ECC (Error-correcting code). Most home/office PCs don't use ECC, so those errors are not detected and cause software failure (like infamous blue screen of death)