I am often asked whether it’s recommended that a person buy the .net and/or .org domain names when they purchase a .com domain name. In my opinion, the simple answer is yes if you are going to develop, but no if you aren’t.
While it’s nice for a publisher to own other extensions when he or she plans to develop the .com domain name, it’s not critical. I would imagine very few people confuse the .net or .org for the .com. The main reason I do recommend trying to get the .org and/or .net if it’s feasible and cost effective is to prevent someone else from competing, specifically if it’s a descriptive domain name.
For domain investors who are hand registering .com names as an investment they later plan to re-sell, I don’t think buying the .net and .org is necessary. If a person has a portfolio of 200 .com domain names, owning the .net and .org of those names is close to an extra $3,000 annually.
Unless you are going to develop and plan to protect your brand, I don’t think it’s necessary. It likely won’t add much value to a deal with your .com and will only serve to significantly increase your carrying costs.