It's been a nice change from the main game, I did manage to come across a little about how the multi player works an sadly it does look like you have very very little control over what other players do so I've decided am not going open mine for random players as it looks like they would have easy access to troll an destroy everything you have done, an the fact they can access the game when you aren't online as well means they could do whatever they wanted while you aren't there to keep watch
It is a pity you don't have more control as the host, I had built four cute little houses so everyone had their own space an I had put six little farm plots outside them too an my work area has all the tables/furnaces/work things with most having been upgraded as well, my base is also level 12, but knowing someone could easily come on, sell everything, destroy all the houses an spend all my gols has put me right off, I don't think they can undo all the builds you have done in town but they can basically destroy your base an everything in it