Of course it is traceable. There is no benefit to spam unless someone is making money. The spam is there to get traffic to someone who is selling something -- they are responsible.
You are correct, in that the email will usually contain a hyperlink to the website of the spammer where they're selling a product or service. The owner of that website can be determined by searching the internet's whois database. Unfortunately, the most unscrupulous spammers usually register their sites via either a P.O. Box or an invalid mailing address, sometimes also using a pseudonym. Makes it a lot tougher to serve legal papers on them.
If you determine that whois contact data is invalid for a particular domain, you can report it to ICANN (Whois data problem report), who will then notify the registrar, who is supposed to contact the registrant and request corrections. How often the registrars actually take action I can't say for certain, but I have submitted problem reports to ICANN and heard back from the registrars that they were taking action against domains for failing to provide accurate contact data.