Real Tech News has disturbing info on what's in your pillow:

Fungal contamination of bedding was first studied in 1936, but there have been no reports in the last seventy years. For this new study, which was published online today in the scientific journal Allergy, the team studied samples from ten pillows with between 1.5 and 20 years of regular use. Each pillow was found to contain a substantial fungal load, with four to 16 different species being identified per sample and even higher numbers found in synthetic pillows.

Sounds lovely :)