This isn't the best picture, but this is the 10 items or less lane - at Walmart.  I stepped up the woman and asked her if she had seen the sign.  She just shrugged her shoulders.  She didn't care who has to wait for her.  She also had WIC vouchers in her hand.  That was bad enough, but I had my basket across the lane and I heard, "excuse me."  "What?"  Another woman said that was her friend, and she was with her.  

Then I got really mad.  I said, "That woman has 400 items, in  the 10 or less land, and you want to butt in front of me?"  "Yeap"  I wanted to deck her, but I just went over to the lane my hubby was in to stand by him.

We got done before this woman, even though there were 3 people in front of us.  I stepped over to that line again, and again pointed out there was a sign that said 10 items or less.  I had to use my outdoor voice that time.  I also pointed out - to the cashier that her friend had just butted in line, in front of me, too.

Be polite.  It's OK to have 12 things, but 400?  Go to another line.