my concern is that the value "created" by startups like uber and taskrabbit come not from displacing large and slow incumbents (e.g., taxi dispatchers & courier services) but from shifting economic risk onto disempowered individuals.
the people who pay (largely the top 20%) see value in at least two ways: (1) greater certainty of commodity products & services and (2) lower prices.
the startups themselves are shielded from market risk, particularly on the supply side (labor), because they have disproportionate power over labor, which then smooths out profit by automatically matching costs to revenues.
taskers bear all the market risk while also giving up traditional employment benefits. the value of this shift is passed on to the consumer and to the startups themselves (capital), leaving taskers in even more volatile economic circumstances.
by the way, i'm distinctly not condemning the startups here, because they're only part of larger economic trends that they have little control over. now that the structure is in place, they can't do much individually (e.g., if one tried to raise prices to raise wages, they would be competed out of the market).