The problem with running lower powered amps with higher RMS speakers is that ppl tend to push the amps to try make the more power hungry speakers louder. Running the amps so high (overmodulating) introduces noise which manifests itself as wild fluctuations in audio frequencies that can damage both the amp and the speakers.

Using a speaker with an underpowered amp is not a hazard in and of itself. Its when humans try to turn up the volume to try make them sound good that can be a problem.