YQL is an amazing piece of technology with robust infrastructure to support it. I was first introduced to it at a Yahoo Hackday in Bangalore and since then I’ve used it to to hack up a lot of small scripts. Like this http://userscripts.org/scripts/show/62104 - one that shows torrents links in Wikipedia movie pages(been couple of years since I updated it)

Christian Heilman was the evangelist behind YQL and it gained a lot of traction with him travelling all around to spread word - http://www.yuiblog.com/blog/2010/02/11/video-heilmann-yql/ . But YQL met with a quick death once Christian left Yahoo for Mozilla. Christian was also in the process of writing a book on YQL - http://icant.co.uk/whyyql/

The only major downside to YQL is that most robots.txt block the Yahoo Slurp & Pipes engine; the user agent that powers YQL. E.g. http://stackoverflow.com/robots.txt

YQL has a lot of hidden treasures. Matter of digging the community scripts to understand.

I continued to use YQL at hackathons in Zynga and stopped it when the primary author Nagesh Susarla left Yahoo - http://nagiworld.net/

Recently a Yahoo engineer told me that YQL is now used internally to power all services at Yahoo. So I am pretty sure it going very strong.