Hey everyone!

I am looking for feedback on this particular example, and any other etiquette opinions/guidelines on the subject in general:
BG: There is a make-your-own frozen yogurt bar in my neighborhood. They have the yogurt dispensers, you get a bowl and pick your favor(s) and put in how much you want, and then go to the wall-o-toppings and pick from there. After you get what you want you take it to the cashier, who tells you how much you owe according to how much it weighs.
The twist: they have little tiny paper cups that allow you to sample the flavors. They also keep rotating their flavors quite often with the exception of the bland-but-dependable staples like chocolate and vanilla. Their flavor switch-outs are the main reason I do not go there hardly at all: I have no way of knowing if they will have anything I like on a given day. I have gone in to get my favorite only to find it gone.
/BGSo today wasn't really yogurt weather but I stopped in to see what flavors they had. I tried four or five that sounded promising. I didn't care for one, I was 'meh' about all the others. Nothing was awesome enough to justify paying for a bowl. So I left...but felt kind of guilty for going in and tasting without buying. This kind of set up isn't like "browsing" through a store since you are walking away with product even if you don't make a purchase. It isn't in any way controlled like the free samples of a particular product that grocery stores will give out. I have been irritated and ashamed to witness the kids from the nearby middle school come out gleefully carrying little paper cups filled obscenely high, laughing at how they got away with free yogurt.

I don't want to be like that - I really only want a taste!

Since the pull-down machines are tricky to work, I always end up with more than I need to get an idea what the flavor is like.
I went in today with the intent to buy -
if they had a flavor I liked, but they didn't. And I wouldn't have known that if I hadn't sampled.
I am trying to reassure myself that the store accounts for "yogurt lost through sampling" in their overhead, but there is that little voice telling me I am "stealing." Am I overreacting?
Can anyone ease my guilt or am I being rude? Anyone want to volunteer what they consider the etiquette to be when it comes to sampling? What about in grocery stores?