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Thanks,
Lucas
I think you may have been slightly misinterpreting the data you have seen. Many people own multiple domains, and point them all to the same page. This confuses the search engines, and they see it as duplicate content, which could cause a penalty. In addition, the benefit of links to the individual domains are spread out, and don't contribute to whatever primary domain the webmaster wants to use.
The solution to this problem is to use a 301 redirect from all the secondary domains to the primary domain. This tells the search engines which domain should receive credit for the content, and directs the link popularity to the primary domain.
There's no real benefit to registering multiple domains and using a redirect to the primary domain, particularly if you're starting from scratch. The main reason this is done is to catch common type in misspellings (e.g. their.com to there.com) or to merge rebranded domains, (e.g. site.net to site.com).