My understanding is that you can buy what ever domains you want. Where you could run in to trouble is if they think your buying domains with the intention of jacking up the price and selling them because you know its valuable to a company. It's called cyber squating. Like if you knew Microsoft was coming out some awesome new product and then picked up that domain name to use against them for $, its illegal.
Typo domains - I don't think they can say shit to you. Have at it buddy.
