How much does it effect the SEO if a .com domain is already registered?

When creating a website with a "brand" name like for example SEO4u and seo4u.com is already registered but seo4u.net/.org etc are free, how much would it effect the SEO of seo4u.com? What are the criteria?

At the end of the day, if SEO is out of the picture, most people associate websites with .com and when they type in the website to visit it, they'll most likely go to seo4u.com rather then seo4u.net

stay clear of brand names in domain names - nothing but trouble as i found out years ago when i recieved a letter from a lawyer after using a brand name, not worth the hassle or cost

blogzandstuff said:

stay clear of brand names in domain names - nothing but trouble as i found out years ago when i recieved a letter from a lawyer after using a brand name, not worth the hassle or cost

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Nice tip but what if it's the same case for non-brand domain names, ex:

WomenLifestyleBlog.com is taken but WomenLifstyleBlog.net/.org is not

For SEO, it doesnt matter at all. Google doesnt give a damn if you use .com or not.

It matters for your clients: marketing, user experience. For this, .com is of the highest importance.