I have a couple well worn memory cards. It seems that they like to break in a way that makes the pcb retract into the shell. I looked at what I could stuff in the back to stop this and found that zip ties do the job.

The extra glue is there to slow down a crack that could break a piece off. The result isn't great, but it's also not too bad.

Here's a picture of a good card — see how the board is held in place by two tiny plastic posts. Great design.