Interestingly, in Massachusetts you can find out the (fairly) complete property records for any address. This includes the names of the owners, sale price and sale history. I'm split by this transparency and efficiency in government. On one hand it is a great way to judge if the price of a home is within reason (by comparing it to similar homes nearby). It also allows you to trace the provenance of a plot of land (in the particular case I was handling the trail ended in 1949) which gives some indication of how clear the title is.
However, this looks to me like an alarmingly public release of very personal information. No one has any business knowing how much you paid for your home, or in fact, going to an address and figuring out who lives there. At the very least you should be required to give up YOUR identity to the authorities and the owner of the property should be notified that somebody is looking them up - openness should work both ways.
In California, interestingly, you can look up the assessed price of a property but you can't see sale price or owner information, which I think is the proper thing to do. You can still get this information by making a request for it, but that leaves a paper trail, which is slightly better. While it is true that sale prices usually exceed assessed prices it still gives you a relative idea. If you got to some commercial websites, however, you can get the complete records.
Usually a web-search with the term "assessor's office" will turn up the relevant websites. Individual cities can have different ways of allowing you to search for data. Malden, for example, is the most sophisticated and easy, allowing you to search along many different parameters, including owner name, property type etc etc. Malden allows you to find plot plans, sale records - basically all legal documents. Melrose only allows you to search by property address.
In Massachusetts all land records (deeds of sale, affidavits etc etc) can be searched for here. This I think is fine, because lawyers can search such records and if lawyers can do it, you should be able to too.