Isn't it funny how gluten free diners become "detail people" whether they've ever considered this skill set part of their natural constitution or not?
Take the case of yogurt. Some of it is labeled gluten free -- and a lot of it isn't labeled either way. 
Consider just a few yogurts produced in the Pacific Northwest, for instance. Nancy's yogurt, out of Oregon, is not labeled gluten free  on the container. Yet there are no gluten ingredients (and I've never had symptoms after eating). Yami yogurt, out of Auburn, Washington, is labeled gluten free. And, in keeping with the trend towards Greek yogurt, Yami has a new Greek yogurt as well, called Zoi. Some of you may remember a previous post when I interviewed my friend Iris, picking her brain about Greek yogurt and the best brands.
As Greek yogurt seems to be enjoying a resurgence (at least two brands are being advertised on television currently), I contacted Dannon, which makes a Greek yogurt called Oikos, about whether it's gluten free or not. 
Here is their reply:

"We sincerely appreciate your interest in Dannon yogurt products and gluten.

We do not use the term gluten free with respect to our yogurts. We separate our products into gluten safe or not gluten safe categories, depending on the specific brand of Dannon yogurt.

Dannon Plain yogurts (Lowfat, Nonfat and Natural), Dannon Plain Activia (in the 24 ounce container) and Dannon Plain Oikos are all gluten safe. However, all other Dannon yogurts cannot be designated as gluten safe because we do not specifically test every ingredient or the overall finished product for gluten."

So, there you go. Now, remember that the FDA has not finally determined the standard for "gluten free" -- so each manufacturer is left to their best efforts. 
Also, my friend Iris informs me that Costco (at least her local Costco) no longer carries her favorite brand of Greek Yogurt, as noted in my interview with her, here.
Happy yogurting!

Greek yogurt: It's being discovered anew: Two major yogurt manufacturers are now advertising their own varieties of Greek yogurt. Why now? Who knows: maybe, after a surfeit of low-calorie this and low-calorie that, people are craving rich tastes.
Every Greek yogurt that I've seen is gluten free -- but one still needs to check the ingredients! For instance, Dannon -- one company entering the advertising fray with its Greek yogurt -- does not at this time give "gluten free" nutritional information on its website. I e-mailed them to inquire. It turns out that while many of their yogurts are gluten free, some aren't. See my post and their response, here. If you are reading this post some weeks or months in the futre, please recheck their packaging, website, or customer service number, to see if anything has changed!
Another benefit of yogurt besides taste? It often includes several different strains of probiotics -- "good bacteria" that help with the digestive tract.
Coincidentally, a few months ago, over a gluten free lunch of clams, my friend Iris waxed enthusiastic over her love for the stuff.  Iris -- a cultural maven with the mostest -- is from New Jersey; and, like many other warm and funny people from the opposite coast, she has opinions on many things!  She consented to share her journeys and knowledge about this creamy treat with us:

Karen: Which is the best Greek yogurt and why?
Iris: Fage is the best because it is the creamiest. I have not checked the nutrition facts with any of the others [something I would normally do] because there is no way I am giving this up! Also, it is gluten free.

Karen: Where does one buy Fage yogurt?
Iris: The best value for this brand is now at Costco. 35.3 oz, Zero fat, is currently selling for $4.99 [Karen's note: at one Costco in the Pacific Northwest; don't hold Costco to this price!] No other store sells this size that I am aware of.

Karen: What distinguishes 'Greek" yogurt from just a regular, full fat yogurt?
Iris: Its creaminess and unique recipe; I cannot find any other brand that comes even close. Also, I cannot tell the difference between Fage's Zero fat and their 2%, and since that's what Costco is featuring, that's what I'm buying.

Karen: what are your 2nd and 3rd choices for Greek yogurt?
Iris: There are no 2nd or 3rd choices....if they stop selling it I will have to give up yogurt. [Karen's note: I have also enjoyed "Greek Gods" brand Greek yogurt; though the container doesn't state the yogurt is "gluten free," I didn't notice any gluten ingredients, and haven't had adverse reactions.]

Karen: When did you first start eating Greek yogurt, and why?
Iris: I have tried yogurt many times in the past and have never liked it. I am very receptive to advertising; so, when Fage came on the U.S. scene, of course, I had to try it -- and all the other "Greek" knock-offs, just to be sure.

Karen: Any other thoughts on Greek yogurt?
Iris: I have to thank Trader's Joe's for introducing me to Fage. . . . 

Karen: Thanks, Iris! Hope to see you soon! 

Note: Photo is unrelated to any specific brand of yogurt; it's just a nice picture licensed by Creative Commons.