Pet peeve
One of the best (and I see all of the time) is exporting data from a Web based application that offer to export in "Excel" format. The file is downloaded and named ???.xls. It opens quite successfully in Excel but when you try to load it in an application that is expecting a "true" Excel format file it fails miserably. When you investigate it is because the export is actually a CSV or tab-delimited text file that has just been named with the .xls extension. The users don't understand the difference they think that because it opens in Excel it is Excel formatted.
Biting the hand that feeds IT
