There are at least three common mistakes involving tricks like this:

1. Alignment. Many CPUs will trap (or worse) if accessing a 32-bit quantity at a non-aligned address.

2. Endianness. Needless to say, the 32-bit value read for a given string depends on the machine endianness.

3. Aliasing. Casting between different pointer types can result in a violation of the C aliasing rules and, with a little bad luck, incorrect results.