A friend of mine stayed at a hotel for a week or so several years ago, and each day the idiot behind the counter did this "freeze" for the current total bill each day. Around Thursday or so, he informed my friend that his card wasn't any good. Of course it wasn't as this idiot was freezing the bill progressively. That is, on Monday he froze $100. On Tuesday, he froze $200. New frozen total $300. On Wednesday, he froze $300. New frozen total $600. On Thursday, he froze $400. New frozen total $1000. Doing this doesn't take long to exceed any credit limit.