My brother taught me that word. He used it in the context of describing his feelings about pesto sauce to me. "First bite tastes great," he says, "after the third bite the thought of eating more makes me sick."
Now, I happen to like pesto sauce, so that particular application doesn't work for me. But I think it is a really interesting word that describes an all too frequent phenomenon. How many times after trying something, anything (a song you hear for the first time, a TV show you see an episode of, a food you try, etc.), you thought this is great! But one or two more "interactions" with the same thing and you never want to see/hear/touch/taste it again.
Malcolm Gladwell in the book Blink tells the story of the Coke/ Pepsi taste tests. Pepsi won every time, yet Coke was the #1 seller. Why? Well, the taste tests were based on users taking one or two sips of each drink - and it turns out Pepsi is hands down better than Coke in small doses. However, buyers don't drink only one or two sips. They drink the whole can. And measuring the taste of the whole can of each drink, Coke wins every time. Turns out that for most folks, Pepsi is cloying.
I think about the concept of cloying when I see new products (and, of course, new websites). Trouble is I find it hard to identify the characteristics that make something cloying or not. At least for me, it truly is a test of time.
Maybe that's the beauty of the web development now (dare I say it - in the Web 2.0 world (barf)). You can figure out the minimally interesting product, release it and see how the masses react. If you do a good job of SEO (or PR or both) you'll get a good batch of testers and see if they stick. If they don't, it's back to the drawing board (although this is now the hard part - realizing when it is time to go back to the drawing board).
Free, real time, actual user feed back is a better alternative to beta tests and focus groups. But I guess if you do go that route, a lot of tests with the same group is required, otherwise you might be releasing a product that is cloying and you won't even know it. .