As someone who,
in the good old days, was the proud ownder of a d100, I believe a number of comments are in order.
A d100 is huge - not something you want to carry in a pocket.
Once in motion, it keeps on rolling. (see below)
Numbers are tiny, which makes it very difficult to use.
They are easy to lose. I owned a d100 for a couple of weeks. During a RPG convention, I used it for demonstration purposes only.
It went...
...off the table...
...down a flight of stairs...
...after being reflected off a wall, down another flight of stairs...
...and lost from sight.
It then either disappeared into nothingness or (more likely) found a new owner among the hundreds of RPGers.
JayBonci is right - not that that would surprise anybody.
Unless you have spare cash, a set of d10s is a much better buy.