Yes, I think very many are dependent on these feeds. As you mentioned, they are the official prices and are referenced for compliance with all those damn regulations and most of the market relies on them so it'd be pretty much impossible to facilitate trading while it's down.

Also, trading in any derivative that is based on any underlying in the feed will be very problematic because that's where the underlying spot price come from. Options trading for example were entirely shut down in those symbols while the feed was down.