EnforcerSunWoo: I think that I would be more concerned of the potential false advertising angle, given that the sale didn't end as stated.
To be honest, it is people being upset and unforgiving why companies over time give out less and less information to customers, so as to never end up being wrong accidentally and having people lynch mob them over the Internet when they had only good intentions all along. The lesson learned from being lynch mobbed might be to make sure that future announcements are very very terse on specifying any specific details to leave a wide wide berth of room for human error. The next Insomnia sale might be announced as:
"Crazy Unpredictable Insomnia!!!!!"
"This incarnation of the Insomnia sale is crazy! It's zany! Our engineers went mad and just threw up games without counting them, and we have no idea how many repeats there will be, how many days it will last, whether or not there will be free gifts or not, heck we have no idea what's going to happen! Anything could happen, or nothing could happen! There might not even be a promo, or maybe there will be, who is to say because... we're crazy!"
That would pretty much cover them on every angle I think.