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Take this stackexchange UX page itself as an example. It contains the StackExchange logo and the words "UX User Experience" (website name) in huge letters.
If you're creating a single-page-application like GMail, you'd want the User to have more space for functionality. Does it really make sense to allow the website name to take up so much space? If yes, why?
As for the logo, I understand that for any brand, showing their logo is of prime importance, but is it really necessary to show it on the top-left corner? Would it constitute a visibility problem if it is shown at the top-right corner of the page or as a watermark at any area on the top/side of the page?