Answer: Social media has a valid purpose as an inexpensive, creative marketplace.
The main point that this passage wants to get across is that the internet, and in particular social media, has become a free marketplace. This means that it can be a very useful tool for entrepreneurs to advertise their products and access a large market free of cost. Therefore, the paragraph argues, social media has a role in modern life beyond the sharing of unimportant postings and uninformed rants.