You have to refrigerate the peanut butter because there are no preservatives (i.e. SUGAR) to prevent the peanut/peanut oil from going rancid. The refrigeration also helps slow the natural break down of the peanut butter, so it lasts longer, preserves flavor and it keeps the oil mixed into the peanut butter.

As far as taking peanut butter to work, invest in some of the smallest ziplock/glad plastic containers (about 1/2 cup) or some Tupperware minis and take a little peanut butter to work at a time. I do this with my butter, salad dressings, etc. and it works really well.