I have very mixed feelings about tombstone projects.
Volunteers go through cemeteries, take the information down off the tombstone - sometimes photographing - and put it on the information up on the world wide web - the Internet for anyone who uses the net to access.
To me this can be culturally insensitive and as I see it, no graveyard that allows it is sacred. Some cultures do not allow picture taking of the living, believing that this takes some of a person's essence or soul and some see tombstones as ancestral and even where the soul rests. THE TOMBSTONE CENSUS TAKERS SEEM TO EASILY GAIN PERMISSION or DO NOT CARE about these things. It makes me question what paying for a sacred space or privacy in death is all about.
The tombstone project volunteers put information up that is less than 70 years old and the US government thinks of 70 years as the privacy zone - thus the 1940 census was just revealed and records in many states are sealed for the same reason - privacy.
Some people have tombstones that have been carved with the name of the spouse who isn't dead yet. This communicates information such as the name of the living person and that they have been widowed. Not private. In some places, not safe at all.
I can't even get into all the ways the information can be used by identity thieves.
MAYBE THE WORST THING ABOUT TOMBSTONE PROJECTS is that they give the FALSE IMPRESSION that the burials with tombstones are all the burials in that cemetery. YOU SHOULD STILL CONTACT CEMETERIES IF YOU ARE TRYING TO FIND RELATIVES, and the Death Record of that person should record if they were buried and where, or if they were cremated. So don't use tombstone information without the death record for your genealogy.
As funerals and cemeteries and tombstones are more expensive, I suspect more people will be going with cremation in the future, unless their religion forbids it.
Please be aware that some cemeteries have no tombstones, or at least many that have been eroded or stolen. There is no national law that says you have to buy one. Many cemeteries have about 2/3rds of their burials unmarked. This can be because no one ever bought a tombstone or because more than one person is in the tomb. Check the rules and regulations for the city, county, or state about this, but in some places a purchased tomb site allows two burials, one atop the other. (In goes the destitute child or the ex wife!)
Also check into the religious beliefs about burials which may differ because a person is Muslim or Jewish, as examples.
I HAVE FOUND A NUMBER OF TOMBSTONES THAT WERE CARVED WITH INCORRECT INFORMATION, including misspellings of names, variations of the name the person was born with being very common. This can give you the impression you have not found the person you're looking for.
Finally, the birth date may not be accurate. In some times and places the date on the tombstone is the date the person was BAPTISED, and the death date, the date they received LAST RITES. Really!