SSL is (should) used for e-commerce websites because of credit/debit card data, but that's not its only use... the data between your user and your server is encrypted, which simply means; if someone is snooping, they'll see scrambled data.
It all depends on what you class as personal/private information, I feel as if passwords are private information that needs an additional layer of protection.
For the folk who aren't very tech-savvy, seeing that green '
https://' in their browser may just make them feel a little safer.
For the (low) cost of a certificate, it's well worth it (imo).
Anyway, it's not for me to decide, I'm just giving you my thought on the matter, like I said... a lot of webmasters don't care/know for it.
Quite a few people are starting to use SSL on their forums,
@DRE,
@MattW and
@RoldanLT to name a few (off the top of my head).