Agree These Are Common SEO Mistakes Made By Merchants
* Dupe Titles (not unique).
* No Text On Category Splash Pages (easy one to blow).

* Product Descriptions That Lack Depth.

I would add these 3:

* No keywords in title or keywords you win anyway (company name or brand). 
* No keywords in image anchor text (or too many keys). 

* No "in-lline" divs promoting "Read More". 

That last one is a "trick" that secures engagement and spider attention by writing 500 or more words and then hiding most of the text behind a "read more" link. 

The content appears to the spider early and the spider skips right on by the "read more". 

Fix these 6 common ecommerce SEO mistakes NOW and you make more money on black Friday.