There is an interesting question that I have seen asked in several locations without a clear answer – what is considered overuse of Schema.org markup? For example, would a local business owner be in trouble with search engines if their NAP was marked up in the footer of every page of their site?
So, at the very least you wouldn’t want to endanger converting actual customers to appease search gods – right?
What To Do?
I’m not 100% happy with the basic solution, it seems a bit clunky from a scaling and long term aspect. If you face any possible downside from duplicated markup then you should only have the data markup on one page. From past experiences you should probably choose your homepage to markup as it is much more likely that it will be crawled more often; you wouldn’t want your NAP markup 5 layers deep into your site structure on the off-hand chance that the page is not seen.
Now, this doesn’t mean to go erase your NAP from the other pages – just have the markup on one single page and keep the NAP on the rest of the pages without markup. This gives search engines what they need and helps inform customers looking for the data.
Possible Repercussions Of Schema Duplication?
The one thing that I have not ascertained, or seen adequately explained, is whether or not duplication of markup is or will cause an issue from an on-site SEO standpoint. If we want to talk entities, it could conceivably be considered spam-ish if it gives extra relevance to a certain location or business – but that is only if schema entities are weighted this way.
Argument For Duplication
If the search engines are able to quickly database and work with all of the emerging schema data there might be a problem. For example, what if your homepage is not shown on the search results, but a sub-page, without markup, is? Will this impact the visual results in the SERPs? Will this affect your CTR?
Personally I wouldn’t worry about this too much. Most people are not searching and looking at the organic results for things like a phone number. They will click through and get it or if searching by name/brand, your data will be shown as it has been associated with your name/brand entity (and your home page is most likely to be returned for a branded search).