I tell my clients that they should comply with CAN SPAM (physical postal address and unsubscribe option) even if the mail they are sending is technically exempt. The bar for legality is so low, there is no reason not to.
Sure, there is a lot of spam out there that does not comply with CAN SPAM. Everything you see from botnets and proxies is in violation, although many of those mails do actually meet the postal address and unsubscribe requirements.
One of my spams recently caught my eye today with their disclaimer on the bottom: “This email message is CAN SPAM ACT of 2003 Compliant.” The really funny bit is that it does not actually comply with the law. Even better, the address it was sent to is not published anywhere, so the company could also be nailed for a dictionary attack and face enhanced penalties.
It reminds me of the old spams that claimed they complied with S.1618.

In accordance with Bill S.1618 Title III passed by the 105th U. S. Congress, this letter can not be considered spam as long as we include: (1) Contact information and (2) a way to be removed from future mailings.

That bill was passed, but never signed into law. That did not stop spammers from adding the disclaimer to spam, though. When I was working as abuse@ we actually treated the presence of the Murkowski disclaimer (the original bill was sponsored by Senator Murkowski) as a defacto sign that our customer was spamming. It was not a bad rule of thumb, either. People who used that disclaimer usually did not have permission to send the mail they were sending. Murkowski disclaimers were common up until mid-2003, and every once in a while they will still be seen in spam.
All readers who may be thinking of actually buying SEO services, avoid Internet-marketing-one.com. They may tell you they will comply with the law, but if their spam is any evidence they do not.

CAN SPAM • S.1618 • Spam • TWSD