Can google ban your site from there search engine for no reason? Surely its there site they can do whatever they want to it...
Absolutely. Although I belive there has been attempts in the past to SUE google by businesses who have suffered drops in rankings. IMO, their site, they can do what they want.
Google isn't under any obligation to include every site in its directory. That having been said, there is always some reason why a site is deindexed. Whether the reasons are good ones is a separate discussion.
For no reason Google can not hurt your site. Especially this concerns banning your site. Investigate what has been recently done - may be you have violated the guidelines or you have had technical problems, hosting issues, for instance.
There's always a reason but the thing is that they will never tell you or give reasons why they took such actions.
Well surely im allowed to ban a users ip if I dont want them on my site? Why cant google do the same....