Paul, I'm having exactly the same issue. When you say "The underlying code that was used is not a Yahoo Finance supported endpoint that can block users at will," are you saying that essentially the service provided by the open data table is unavailable to everyone when this error message occurs? In that case, is the table being blocked because the total volume of usage from all users is too high?
I've tried to use this open data table with a modest number of requests - just a handful per day - and found it to be blocked so often as to be unusable. At the same time, I've noticed that calling it from the YQL Console and from my application often produce different results - one works the other doesn't. I'm having a hard time understanding why this might be so, as I am certainly far under the YQL limits in any event.
Thanks!
Peter