There is a class action lawsuit on behalf of owners of Macintosh computers that use MagSafe power adapters. If you own such a computer but have not received a notice about the lawsuit, find more information at https://www.adaptersettlement.com/.
As this relates to power cords with frayed connections, this is an issue that should be taken very seriously. Regardless of manufacturing quality, the helpdesk frequently sees frayed power cords for laptop computers. Here are a few recommendations:
1) put a loop in the cord before winding it up
2) be careful to not leave cords where they will be stepped on, or rolled over by chair wheels
3) if you see exposed wire or stressed wire covering (typically near the ends of the cables), do NOT use the power adapter
Apple recommendations – http://support.apple.com/kb/HT1630 (their advice applies well to many makes and models of power adapters – not just MagSafe adapters)
Have questions? Contact your computer vendor. Or the helpdesk (especially for college-owned equipment).