I had a skein of Buffalo Gold's Lux yarn - in Yellowstone (green and gold), one of the special colorways dyed by Lorna's Laces. I wanted that colorway because it is Colorado State and Dallas STARS colors. I saw the cutest scarf designed by Evelyn Clark called Wildflower Lace Scarf at the Fiber Fest last April; so....
I was knitting along happily, using a size 2US needle, but didn't take notice that the Addi's size 2 needles are 3.00mm, not 2.75mm, as the pattern suggests. I tend to knit a little loose (and I did notice that my scarf was looking a little wider than the model from what I remembered). I was worried that I wasn't going to have enough yarn to finish, but reasoned that usually, when knitting along in a looser gauge, it takes fewer yards to get the length desired. However, I forgot to take into account that the pattern has a set number of rows and a set number of repeats...I kept knitting, until I was 3/4ths of the way finished. At that point, it was apparent that I was not going to have enough yarn to finish the scarf.
Since I didn't really like the gauge of the fabric I was knitting, I frogged it on Friday and started again on 2.5mm needles. (Remember, I do tend to knit a little loose...) I think it is coming out just fine.