The biggest reason to vary from the 10% rule is if there are a lot of callers in before you. Say half the table limps and you do as well, then the button raises it to 1/6th your stack. If the other 5 people call, you're probably best off calling as well because you aren't just playing against one person. You can make more than the size of your stack, so you can call a larger bet.

If you're the first/only caller, then the 10% rule becomes fairly solid IMO.