AI companies typically build their AI models on lots of publicly available content, from YouTube videos to newspaper articles. But many of these content hosts have now started to put up restrictions on their content.

Those new restrictions could bring about a "crisis" that would make these AI models less effective, according to a new study by the Massachusetts Institute of Technology's Data Provenance Initiative.

The researchers performed an audit of 14,000 websites that are scraped by prominent AI training data sets. The intriguing result: that about 28 percent "of the most actively maintained, critical sources" on the internet are now "fully restricted from use."