Since there is no central authority Governing Bitcoins, no one can guarantee its minimum valuation. If a large group of merchant decide to "dump" Bitcoin and leave the system, its valuation will decrease greatly which will immensely hurt users who have a large amount of wealth invested in Bitcoins. The decentralized nature of bitcoin is both a curse and blessing.
An example of such ''large group of merchant" will be institutional investors, obviously they have invested quite a lot in the network over past one year, but that doesn't give them control, even if they 'dump' their coins and exit the network, the effect of that can only be momentarily/short term, Bitcoin is a sustainable network, and users should understand that manipulations/dumps/plunges/corrections are only short term, and except for the investors that want to make 'quick buck', it doesn't necessarily hurt.