I'm not familiar enough with the details of database theory to judge whether it's possible or not, but I'd guess that it would be safe to undo an action if no later transaction has read the data the user just touched and made other changes after having read it. Ease of Maintenance Joe Nerd doesn't have spare time or money for installing and maintaing a database installation. Instaling it and making sure it keeps running smoothly. Installation should be completely straight-forward, and have reasonable defaults, so you don't even have to change any parameters before installing it. It can surely be done.
Databases often get slower and slower as they get bigger.
In summary, I believe that the twin effect of new users starting to use databases for new things will have a profound effect on the database market.