Too much on the Internet is based on "trendy", flavor-of-the-week thinking, where everyone tries to pander to every momentary craze that comes along. People's choice of domain names often reflects this, with little thought of the long-term sense of what they're doing. When you register and use a domain name, you're adding to the permanent infrastructure of the Internet; you should think this way. Once a site is on the Web, there will be links to it forever (there are still sites linking to long-obsolete addresses of my sites), so you should try to put some foresight into making something that will be meaningful for a long time to come, not just for the lifespan of a mayfly.
In this spirit, you should generally avoid embedding short-shelf-life references into your domain names. Let's say you run a convention called FooBarCon every year. The next one will be FooBarCon VII, to be held in 2003. Resist the impulse to register a domain for it like foobarcon2003.com or foobarconvii.com... that'll be yesterday's news as soon as the '03 con is over and you're working on the '04 event. Better to get a general name like foobarcon.com (or foobarcon.org if it's a nonprofit event!) that you can use year after year. Use subdomains like vii.foobarcon.com if you want separate sites for each specific event.
One big benefit of the long-term approach is that you don't get saddled with heaps of no-longer-useful domains that you have to either keep paying renewal fees on until the end of time, or else face the indignity of possibly having a cybersquatter grab them after they expire and putting something embarrassing like pornography there to ensnare anybody who follows lingering links and search engine indices of your old site. This fate has actually befallen a number of organizations. If you stick to names with permanent significance, you'll have a much more manageable task keeping them renewed. And if you make effective use of subdomains instead of getting a new domain for every temporary gimmick, you'll have addresses that nobody can ever cybersquat.
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