Surfing marijuana sites is generally protected by the First Amendment to the U.S. Constitution. While it is generally against federal and most state laws to use or sell marijuana, you're within your right to talk about, write about and discuss marijuana on most Web forums. It is generally safe to register for an account with message boards and other sites that discuss marijuana use if those sites don't engage in the sale or distribution of marijuana.

On the Other: Stay Away From Medical Marijuana Sites

Avoid registering with sites that purport to sell or distribute marijuana for medical reasons. While legal in some states, medical marijuana still violates federal drug laws. By registering on a site that sells medical marijuana, you create a permanent record of your involvement with a group that engages in potentially illegal activity. If you make a purchase on a medical marijuana site, your financial records are at risk of being seized by the federal government and potentially used against you in court.

Bottom Line

It's OK to register with sites that simply discuss marijuana use and cultivation, but be careful what you write: Posting on the Internet leaves a permanent record, and that record can be used against you in court. Avoid sites that sell or distribute medical marijuana. These sites operate in a legal gray area and occasionally come under prosecution from the U.S. Attorney's office. You don't want your name associated with a federal drug investigation.

Source:

Medical Marijuana: Your Rights

Rules about Marijuana on the Net

Resource:

Ya Hooka: Guide to Pot Laws on the Web