Double-sided Printing -- Several people wrote to warn against printing on the back of already-printed sheets of paper, as recommended in TidBITS #175. Joe Gurman relayed information from a repair person who claimed that some high-speed printers (the one in question was an older Ricoh engine used in the Talaris 1590 printstation) were more likely to jam when using reused paper because of changes in the paper when it was exposed to the high heat in the laser engine the first time through.
Another reader claimed that some laser printers contaminate the paper with small quantities of fuser oil, and reusing printed paper can cause this contaminant to migrate to places it doesn't belong, such as the rollers that grab the paper. If anyone knows for sure about this issue (in other words, if you're a printer repair person or printer engineer, not just relaying a possible computer legend) please let us know and we'll try to settle this issue once and for all. In the meantime, if you wish to play it safe, check with your printer manufacturer.