If you live in MA (or TX, SC, FL, GA, AL, TN, or CO) and use a Firewall you should beware. It may become illegal if bills in those states pass. I just downloaded the MA one and am going to read through it tomorrow, but the blog entry linked to above says:

Here is one example of the far-reaching harmful effects of these bills. Both bills would flatly ban the possession, sale, or use of technologies that "conceal from a communication service provider ... the existence or place of origin or destination of any communication". Your ISP is a communcation service provider, so anything that concealed the origin or destination of any communication from your ISP would be illegal -- with no exceptions. [Freedom to Tinker]

Just to explain that a bit more. That would make most corporate firewalls illegal, along with those little mini firewalls they make for home. And don't forget just about any recent OS (since they do connection sharing). (via BoingBoing).