often we have been seeing and making the websites , responsive ones on the perspective of what looks how in the order of its small screensize:

Responsive designs are taking the rude idea of fitting the messy desktop design in to mobile by adjusting it to its size and variability.. And persuade the clients to go with the app later which could serve the purpose.

If you are using the same strategy for the ecommerce website, you are doing it all wrong..you need to have a solid ground work on what looks better in the mobile for ecommerce, placement of elements, adjustments , products, cart etc and then extend it to desktop: I have experienced huge variation trying this method out and vice versa: Any comments which oppose this statement are highly welcome , knowledge sharing is valuable to the core