I believe it is if you do not disclose any identifiable information about yourself while using it. You must also use privoxy to limit the amount of information your browser broadcast about you and your machine information. You must be careful with java and other tools the website you visit puts on their sites. Some of those tool will be able to identify you if you are not very careful. I will put this additional limit on its abilities if any three letter agency wants you are not going to be protected as there are to many others ways to find you and get the information on your computer. However if used properly I believe tor/privoxy is an excellent way to make yourself anonymous on the Internet provided you take the above simple precautions .