Helpful Hints from joeeze: How to fix a credit card that won't swipe

Wrote Judy Dutton in Wired:

A credit card is like a cassette tape: it slowly gets garbled from overswiping.

The reason: both the tape and the magnetic stripe on the credit card are made up of millions of iron-oxide particles that convey information by generating electrical pulses in the reader.

With wear, these particles get smeared, creating background noise. Luckily, this noise has very low magnetism, and it can be dampened by increasing the space between the magnetic stripe and the head that reads it.

So simply cover the stripe with Scotch tape.