Adding it to your TOS and/or disclosing it on forms (pages) on your site covers things for you. You may want to also include it in the order email or welcome email - it's like a little history about your company or something.
When marketing, it's not necessary, but you must note that on your TOS and AUP - "Hosting company LLC" doing business as "Host company" and so on.
If you don't present it on the site and logo, you must show it on the sign up documentation to they know legally who you are.
Hope that helps.
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Where I come from, you're legally obliged to have it in your official company stationary (letter heads, legal documents, etc.), but its certainly not necessary in your logo or prominently on your website. If you choose to put a copyright notice at the bottom of your website, you might want to include the full company name there.
I tend to think that companies who put their suffixes in their standard marketing jargon (i.e. in the introduction on their front page) are just being unnecessarily verbose. Sure, its nice to know the company you are hosting with, but that sort of information should really be found in the Terms of Service. Thats just personal opinion though!
Check the company laws in your country, the requirements might be different.
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