I thought they can delete your creations on here aswell?
In Blockland, there's a trust system, and a minigame system.
There are 3 levels of trust, None, Build, and Full.
When you ask someone to increase the level of trust, they must agree to it. Both players must remain at equal trust levels, or else it drops to none.
If someone asks you to increase the level of trust, you can either accept, decline, or ignore them till you decide to unignore.
With no trust, they cannot do anything at all to your bricks, unless they're an admin. But then they can only look at wrench properties, and clear them.
With build trust, they are able to set wrench properties, and build on your bricks. They cannot print on, spray, or destroy your bricks. They are also able to push and enter your vehicles.
With full trust, basically anything can be done, they are allowed to set events on your bricks, break them, spray them, print on them, and everything else.
In minigames, if all players' bricks are included, and you aren't the owner, players can use your vehicles, and 'kill' your bricks. 'Killed' bricks will respawn after some time, so nothing is actually lost. If you are the owner, you have the option to turning off brick damage, and the option of disallowing others' bricks (which includes items and vehicles) to be used.