Financial dealings on Shabbat - or at least goods: borrowing without saying "borrow." If Erev Pesach (in Jerusalem in the time of the Temple) fells out on Shabbat, certain negotiations could be done for the sake of the korban pesach. Also: Several cases based on the mishnah's concern re the specific language of the loan, which leads to the difference between a larger, longer-term loan vs. spotting someone for a short time. But isn't the shorter-term loan at risk of getting written down? During the week, the language is less significant, but on Shabbat, the language matters. Plus other cases between Rava bar Rav Chanan and Abaye, whether one must use a shinui (difference in practice) for certain practices, and when one is not required. And: we avoid certain practices to guard against coming to fix an instrument, but people do those practices! And people don't correct them! Better that people do what they're going to do anyway and not be rebuked so that they're not violating the halakhah intentionally. But why prohibit it if people aren't going to keep it?! Alternatively, there's a paternalistic assumption that they're not going to do the right thing, why not give people more of a chance. Also: The principle that halakhah follows the anonymous voice of the Mishnah. And: Don't write down your guest list or your meal's menu; keep track in your mind. Likewise, people can draw lots for some aspects of who gets what at a meal, but not the size of the portion.