I could answer this in one word, NO!

I mean - say I had registered www.micro-soft.net years ago, would it be a threat to www.microsoft.com? No of course not! It would have been some geeky poxy blog or something with sod all to say, versus one of the richest wealthiest companies in the World.

Similarly you get a good idea…I had one the other day, I'm going to sell fantastic tools for internet marketers for a buck, so I registered www.1dollaronly.com - but is it me worth me registering www.1dollaronly.net? I can't see any reason why I would do that, at all.

People go on at me about protecting a brand, but what's the problem? If someone makes a better site than you on a variation on your domain name, then you have a crap site and you need to sort it out.

Search engines used to be bothered about domain names, now they don't care, look how well Wikipeadia ranks for almost everything under the sun.

So in short, IMHO, if you buy a domain name, buy a good one and then build a good site, you can't go wrong!

If you think different, please comment below.