Sometimes people sue for the principal of the matter, not because of the amount. I think if Target was aware, for months, about this 'glitch', they should have some repercussions. When you take into consideration how many times they got away with profiting off of this glitch, that amount could be very significant in favor of Targets profits. Perhaps the person suing is doing so because they realize this, and maybe she is doing this on behalf of everyone being ripped off, and/or the mere fact that target is being unethical. Someone has to stand up for what is right.
Personally, I don't always go over my receipts with a fine-toothed comb--mostly because I usually purchase large amounts at a time, and if the difference isn't obvious and 'stand out' I simply don't always notice.
Also, some stores do have receipts that are very difficult to read. Not saying that Target's are-- but there is one store, can't recall which one at the moment, that if you use a coupon, instead of taking off the total price of the coupon at the end, what this store does is take a little bit of the coupon price off each item you purchase. If the item was also on sale, I'm telling you, you have to really study that receipt hard in order to see if you were charged correctly. Most stores are not like this, but some are. Perhaps they make it so confusing because they don't want to make it easy for people to notice if something was rung up incorrectly. Much like trying to decipher some of the bills that come in the mail. DH and I are both college grads and we are not totally ignorant, yet there are things we have difficulty reading, and we also believe that some businesses know exactly what they are doing when it benefits them and not the consumer. It's not always a slip-up.
I've never sued anyone, but I actually think it's a good thing when people stand up to businesses on principal. Everyone should be happy about it because they are representing all the little people.
*That's not to say that there are some really frivolous lawsuits out there---I do not agree with those at all.
Just my 2 cents.