The video at peekURL.com/vzfn684 shows Rachel Maddow lying to her viewers about the provisions of the new Arizona immigration law. She says:

It's remarkable legislation that requires police officers in Arizona to demand the paperwork of anyone they think looks like he or she might be an illegal immigrant... ...[Referencing Jan Brewer's comments] There will be no racial profiling in Arizona... except for the part where police officers now have to stop you if they think you look illegal.

Rather than repeat myself, please see this post about CNN lying using highly similar lines. Anne Kornblut and Spencer Hsu and Ted Robbins of NPR have also retailed this lie.

Maddow also references legal immigrants who "aren't carrying all of their immigration paperwork with them at the time", gesturing as if it would be a large amount. Contrary to the impression she's trying to give, a green card is actually a small document. Further, as already pointed out, legal immigrants are already required by federal law to carry their green card or similar.