Infinitesimals
Voicemail has its uses, for example, when one won't be able to pick up the phone for awhile, but needs to relay a message immediately, or when other forms of communication are not possible, i.e. e-mail or texting is inconvenient or irrelevant.
However, I still usually end up ignoring it, thus rendering most of the pros as moot.
On the subject of high school friends, just because you're different, doesn't mean you can't be friends.
Well, actually, maybe it would just be better to use what is currently known as 2*pi. I've always thought it would be easier if sine and cosine had periods that were just pi, not 2pi.
So should pi be 6.283185...? Should pi be the ratio of the circumference of a circle to its radius, instead of diameter? If so, it would take about 50 years for this to gain any momentum in the mathematical community.