I have not had any issues with my clients. We send the product through with hashes like http://neat42.com/tshirts/1-faded-short-sleeve-tshirts.html#/color-blue and canonical all of the pages without the hash. If you can control the quantty through a url string you will not have any issues.

The images on Wikipedia are actually Wikimedia images and covered under the creative commons rules. You can read more about the required attribution here, https://commons.wikimedia.org/wiki/Commons:Credit_line

This might help.

http://googlewebmastercentral.blogspot.com/2012/08/configuring-url-parameters-in-webmaster.html

I personally would use both. They way that I look at it with the OG tags is that you are controlling the consistency of the brand across platforms that you do not officially support. This is very much in my mind the same thing as making a page display correctly in older version of IE.

I would say it is not good practice. I think of the heading system as a structure system. Like a book or an outline. The h1 tag should be the title that encompasses the whole page. The h2 tags are like the chapters, h3 are sub chapters or strong points inside the chapters and so on.

I have become frustrated at MOZ in the last few months, none of my backlinks have made it into the index. Old back links. Long story short, I figured out the issue and I figured out how anyone can manipulate their DA. I wrote a blog post about it here, http://blog.dh42.com/manipulate-moz/