The trend towards self-organization of systems like peer-to-peer or ad hoc networks generates increasing needs for designing distributed storage schemes that should themselves be self-organized and cooperative. Unfortunately, in such systems, the data stored are exposed to new disruption attacks either because of the selfishness of participating nodes with respect to their resources or even because self-organization that leaves such systems much more subject to maliciousness. This setting, combined with the high churnout of nodes and with the high chances of network partition, particularly in mobile ad hoc systems, makes it quite uneasy to ensure the long-term availability of data stored in such fashion. This paper discusses a verification framework based on the probabilistic assessment of small cryptographic verifications in order to assess storage and to prevent data destruction. A protocol for determining the availability of data stored in an ad hoc fashion is detailed. The design of a reputation system based on this protocol and inciting nodes to cooperate towards storage is then discussed.