I consider myself a pretty reasonable person. I don’t mind a knot in a skein of yarn once in a while. After all, the mill making the skein/ball of yarn winds the yarn from a much bigger quantity, and will occasionally run out, usually not at the same time as the time that the ball is finished. I would rather have them tie a new one on, if that is the only method they can come up with for re-attachment, then have only half a skein. But then I started a new ball of Universal Yarn “Star Light” earlier last week.
Now, I know that my rounds are not short, as this is the yarn that I use for my Oregon Shawl. This means that there is just shy of 900 or so stitches on my needle. But I have had to re-attach this ball of yarn now for the 5th time. Just so we are clear, this is because I have run into 5 knots, within 3 rounds… It is like they emptied the bin of cone ends into this one ball. To be completely fair, this is the 3rd ball of this yarn I am knitting, and I don’t recall any knots, or maybe just one, in the previous 2 balls. And no, I am not taking this ball back, because I am finishing Oregon for a dear friend, and she gave me the yarn she was using. I just really hope that this is going to be the last time I have had to attach this yarn. If you would like to know the rest of my opinion on this yarn, I invite you to look at my post about it in early May. I just read it over again, and was actually surprised to realize my opinion of it has not changed significantly, provided I won’t find a lot more knots… 
If I do, you can be sure I will let you know.
I know just what you mean. I hate it when I’m cruising along on a project, then start with a ball that is full of knots. It happens a lot when I’m working with Knit Picks yarns. So frustrating to have to keep stopping to join.