Honestly, I'm not a fan of purity rings in general.
I realize that they're helpful and inspiring to some people, and that's great, but I do have some issues with them:
1. As others have noted, there can be confusion, depending which finger they're worn on, with purity rings and engagement/wedding bands.
2. I disapprove of how in some circles, teens are pressured into wearing a purity ring and making the associated vows. Don't get me wrong, I think chastity is an excellent thing (and I personally distinguish between chastity and purity), but I also believe vows are meant to be taken seriously. I don't like the idea of a teen or young adult being pressured into taking a vow they don't mean to keep. And let's face it, in those certain circles, for a teen to say "Nope, sorry, I'm not doing the purity ring thing" would be very ill advised.
3. The "Purity Balls" can be kind of creepy, IMHO. There some patriarchal baggage underlying them that makes me very uncomfortable. (Your mileage may vary!)
That said, I do have a ring set that I bought secondhand, that looks like an engagement/wedding band. With my job and some of the situations I have to navigate, it's often much easier to let people assume I'm married.
I don't wear it socially, though, and I don't see a problem with wearing it at work, if it reduces the amount of unwanted attention I receive. At work, I prefer to avoid both men making passes at me and people making assumptions about the reasons I'm unmarried at my age - such as what my sexual orientation might be.