Brendan Eich posted here that he was in fact blacklisted and could not get funding for his Brave start-up for several years.

The Hollywood blacklist was also maintained by companies and not the government. It really doesn't make a huge difference who's maintaining it, if enough employers / financiers ban employment / financing based on it.

Cory Doctorow refutes the idea that corporate censorship does not matter in their essay "Inaction is a form of action".