I would be extremely careful about doing such. You could easily be coined a cybersquatter and end up being sued (or worse.. losing the domain as well as being sued). This is no laughing matter. If you choose to go down this route, I'd recommend you find yourself an attorney that is competent in domain name law.
It's hard to really say whether some of the companies may take action against you or not... It really depends on what type of names you registered. Something like Microsoft.mobi, MicrosoftUK.mobi, etc would be ground for a serious lawsuit against you, whereas something along the lines of fish.mobi (intending to sell to the fish.com owner) would not be.
If the words are generic, you're alright. However, I'd advise you not to go around registering brand names -- it's not worth the trouble...