One of the things I look at when evaluating domain names to acquire is how many other TLDs are registered for that keyword. Obviously, the more domain names that are registered, the better. In addition, I also look at very similar keyword domain names, including those that use the same keywords with additional words (ie DogWalker.com and BostonDogWalker.com).
Taking this a step further, I also have a look to see who owns the other extensions and when they were registered. It’s always good to see that Name Administration or another successful domain investor owns a keyword name in an alternative extension because that is indicative of a good name.
Even better, though, is when a company or person in that particular field owns one of the other extensions. If multiple companies own different extensions in the keyword, it’s even better, especially if the registrations are aged (5 years+).
First off, those are great sales prospects should you want to sell. Secondly, it shows the keyword has value to companies in the field, so you might either be able to sell it quickly, build on it if you want to spend the time/money, or wait for the right offer to come around.
Finally, when you buy the .com and there are other developed extensions, you’re likely to receive traffic as a result. This traffic is fairly well targeted and can be monetized in a variety of ways. It can also be used to show potential buyers the value of buying the domain name from you.
Buying the .com domain name when there are many other TLDs registered will likely cost significantly more money. However, there is considerably more upside to these types of names.