Much harder to rank within contained hosting platformss. Google doesn't give as much credit to "sitebuilder" platforms due to it being easier to spam for ranking.

For exmaple: if I am running a roofing company in St Louis, I can quickly and easily create 100 sites on weebly about roofing companys, roof repair, etc. On a real domain and full website, its harder and more time consuming to do that. A "normal" or natural site would not be set up that way. Google knows that legitimate sites put in the extra time and effort in making their sites worth a users time, and ranks them accordingly. Also, you don't want to pass your ranking weight to weebly, best to keep it on your own platform.

That's the short version. Just don't do it, lol.

"Should the 301 redirects map the canonical URL on the old site to the corresponding canonical for the new design . . . or should they map the non canonical database URLs old and new?"

Any URL's that are indexed should be redirected to the correct version. For example if you have both a database URL and a canonical URL both indexed in search results, then they both should be sent to the correct version.

Also, having only canonical URLs in your submitted sitemaps will help to remove a lot of these, even without redirects.

I think it comes down to a few things:

1. How many products are you going to offer?
2. How do people search for this product or service?

Personally, I like the "websitename.com/shop/keyword" format because it flows better. This is the same type of URL structure we use on a client that just joined. This also allows us to separate the normal site content from the store, as you can see from the top links. These do not include "shop" in the URL structure.

http://www.grandsierragloves.com/shop/mens.html

If the content is viewable on the mailchimp database, and is set to index then yes it could hurt you.

I highly doubt this is the case. Most likely the content is not set to index, and you should be able to post it on your site without an issue. Might even help, since users might search for that exact subject after receiving your email. Make sure to add in authorship info so Google can tell yours is the original article, not any others if there are any.

Always link by page and subject matter. If you have an article about red widgets, you should link back to the page you have about red widgets. True you can build up your home page with a lot of links, but this hurts your user experience by making them have to go through the entire site to find what they came there for.

When you send all your links to the homepage, you are suggesting what page is the most important to search engines. This can often be seen where you have sites that never have any subpages ranking or showing up in search results, only the home page over and over. Sounds great doesnt it? But you can limit the exposure of your site in the long run. By directing links at your subpages, not only do you increase the chance that they will eventually rank higher, you also can get more specific with your linking text.

Direct keyword linking to the home page is more risky. With your subpage links, you can get closer or even use exact keyword phrase links because the content is more specific. In reality, use whatever link phrase that a user will click on. A bunch of keywords might not do that job as well as a conversion statement. If you are worried about getting people to your home page, change the way the subpages are set up on your site, so that users can go to the other relevant areas of your site with ease. It should be easy and simple to direct them where you want them to go using graphics or styled text.

You can use the hashtags and query strings to display the content, just be sure to specify the URL parameters in Webmaster tools so you dont have multiple URLs getting indexed.

Go for the user. If you look at seo-browser's reports for pages that have large images or fullscreen sliders, it still renders out to a search engine bot about the same. People like pretty. People share pretty. We use a full screen slider for our home page, and still rank consistantly on page one.

Even better if your large images are conversion-focused. Might actually see an increase if done right, rather than a ranking loss.