1) useless tags will always be added, the site is growing everyday so there will be more and more people adding useless tags.

True. The 'deletethistag' alias will keep the oft used 'useless' tags under control though.

2) if you really think the tag is useful then you will have to maintain it

That would be the 'faults' tags with me.

3) I don't want to see moderators spending hours adding/removing tags because of strict policies.

hardly see it as a strict policy though. We're not like (d)Danbooru...