Vertical marketplaces that involve fractionalized labor (eg, tasks, gigs, freelance work or short-term assignments) are particularly interesting. These fractionalized labor marketplaces have three key advantages over pure job sites that are focused on full-time employment. First, the fractionalized labor marketplaces tend to have high repeat usage on the supply side because the workers come back frequently to find the next money-earning opportunity.
— Read on medium.com/craft-ventures/linkedin-is-the-new-craigslist-39e71238e995
Fractionalized labor is a fancy term for piece work. It works best for companies when there is as large undetemployed workforce that will come back for more time and again.