This may be a very dumb question and if it is… my apologies. 
So, I’ve been reading a bunch of Google forums about my website which has recently lost ranking and a number of people (who may be experts or just average joes) claimed that my site is getting punished for duplicate content on the same server. The thing is, I host my shopping cart on my server but along with it, I host two addon domains that are blogs used to push traffic to my cart through content rich articles. They claim that I am hosting the same sort of general content on the same server and Google has caught me for it.
So here is my question… in v4, you have one database or one back end but multiple storefronts, right? You could essentially have one backend with 10 products that 2 or however many stores “share”, correct? Well, if 2 stores share 1 product with the same name, description, price, isn’t that the same as 2 pages of duplicate content when both of which are hosted on the same server? It seems obvious to me.
I just want to know what the difference is before I invest in moving several sites over to v4 and possibly furthering damage my reputation with Google. 
Thanks.
It is my understanding that the multiple store fronts are hosted on separate DOMAINS and therefore are not considered duplicate content.
A duplicate content complaint by Google would be multiple pages (containing the same content) indexed due to canonical URL problems. It isn't so much that Google “caught” you for this, as it is each duplicate instance of the page reduces each page's relevance - after all, Google isn't going to list them all.
IF your blogs and store are on separate domains, it sounds to me like you got some bad advice on the forums. I don't think Google gives a rats about the shared “server”.