Why don't Yahoo News articles pinch-zoom anymore on an iPad...?

This is just a guess; I don't have an iPad to verify. The designer may be using a responsive design to serve the page to different devices. That requires using a "viewport" tag in the header of the page code. In order to enure that the design doesn't break when zoomed, there's a setting that can be included called maximum-scale. If that is specifically set to a value of "1", then the ability for the user to scale the page is removed. Good for the designer, bad for the user. As far as I know, the only way around it is to use the desktop site.

Are they maybe using a Yahoo-specific app, or pointing their browser directly at a mobile version of the site? If I type "news.yahoo.com" into Safari on the iPad I can zoom articles just fine. It does appear that some sites block the zoom function on mobile devices. A workaround for that could be mapping the Zoom function to the Home button via http://support.apple.com/kb/HT4064. That way, triple-clicking the home button toggles a zoom function, just like how double-clicking produces a list of recently open apps. Then with zoom turned on you can drag the viewport around with three fingers. It's not ideal but it might help.

Yes, you are being hit by a horrible iPad-specific site that doesn't work very well (like most iPad-specific sites. I don't have a clue why everybody is switching to them.). On the main news.yahoo.com site, there is a tiny, grey "View Desktop Site" link in the bottom right corner, which should theoretically solve your problem. That link doesn't seem to appear on individual news stories, though, so you'll have to go to the main site. I just tried and failed to get the "View Desktop Site" link to actually work from the main site--it reloaded the iPad site the first two times I clicked on it, and the third time it crashed Safari. But, theoretically, that should work. However, in my experience, you have to click on "View Desktop Site" everytime you visit a site because they all default to the iPad site, and I doubt your friend will be able to find the tiny, grey link on their own. If I were your friend, I would compose an annoyed note to Yahoo News pointing out that their new (horrible) iPad site is not accessible to all readers. Maybe they'll get rid of it and just let us all read the desktop site, which would be vastly preferrable.

Thanks for the answers, hivemind. I wasn't able to find a "view desktop site" link anywhere on Yahoo News, but I think the "reader" function on Safari *might* work well enough. Chrome seems to have an easy way to request the desktop version, but that solution will require some user adaptation to a new browser. I'll see if it's worth that effort if the "reader" thing doesn't work out. Thanks all!