Ann: Red 5 and Silver Lake Resources to Merge, page-283

Discoveryman - to completely take over a company, you need to get at least 90% of the shares - once you've done that, you can compulsorily acquire the rest and then you own 100% of the company and can do whatever you like. As such, any shareholder owing 10% or more of the shares can block such a 100% takeover.

By contrast, someone can acquire 50% or more shares and then appoint 50% or more Directors to the Board and effectively run the company. HOWEVER, they have to be mindful of the rights of minority interests, so those controlling the company with their 50%+ shareholding can't for example simply transfer assets to other entities they own at will nor raid all the cash held by the company they "manage" (well, not legally anyway).

I hope this clarifies things.