Should I report spam?
Some spam is impossible to trace or it is not use because they are in a country that really do not care that much on what people do. So if you leave that out of then you have the normal spam you tend to get on Craigslist or email from local companies.
You should always (if you have the time) report spam because only if we all do it we will maybe finally stop it or make it harder for the spammers to continue working. Facebook for example have won several big cases against spammers and they will not be spamming any time soon.
An easy way to report spam is to use Spam Cop because they will do the work for you and that will save you time and money in the end. They will also hide your real email address from the spammer.
You only need to confirm your email with them and fill in a small report and they will take care of the rest for you. If they have any more questions they will contact you again.
I have used Spam Cop more than once and they do a really good work and it is totally free.