A few months ago I was having lunch with our trademark/copywrite attorney and he mentioned a similar case he where he had just won. A company, XXX Travel was promoting vacations for people in the "Lifestyle". As it turns out, his client, XXX, provides these very same services and he was able to prove that the intent of XXX Travel was to siphon off traffic / business from XXX'a travel business. The trademark infringer was forced to surrender the domain name to XXX. I was not provided any other details surrounding the case. Given this, and other materials that I have read, cybersquatting is not looked fondly upon and legal outlets, while still in their unrefined infancy, are coming available and if you should register a competing domain to an established brand, it is possible you could be subjecting yourself to an expensive amount of litigation, especially if you have even remotely similar services.
In the case you give with Microsoft, they have an enormous legal budget and can file a suit whether or not they really have a leg to stand on. If lets say you were able to register that domain name, microsoft.net and were NOT in the software (or even Information Technology) business...lets say you were selling a new type of toilet paper; they would STILL file suit as they MUST always be able to show that they aggressively protect their trademark (a requirement of the trademark office). This means that you would have to respond to their suit. This typically involves a minimum of a 5-10,000 dollar (or more) retainer for a lawyer to defend you/your company. This is less than a drop in the ocean for Microsoft; but for most other folks, this could be a tremendous financial burden. If you chose to not respond to the suit by the designated date, they could win a default judgement against you (which could include the surrendering of your domain as well as monetary penalties).
We at OroLatina.com believe strongly in protecting our own trademarks (OroLatina and OroLatina.com) and respecting those of others. Without this sytem in place, anyone could represent themselves as (or close to) anyone else they would want.
In short, avoid legal entanglements, especially with the big players in the markets and create your own, unique name and brand identity for whatever service you choose to provide within the market place.

Cheers,