The paper presents BOINC, a software similar to SETI@HOME for using home users computational resources.
A common problem with this approach are the incentives for home users, which the current paper addresses through the use of "credits" for computational power (which may be rewarded) and by allowing users to select computational topics they feel stronger about.
An interesting discussion point is the use of total energy of this approach compared to a dedicated cluster (a single organizational control). For example, BOINC launches multiple redundant tasks to avoid malicious results, which is clearly a waste of energy. Also, these tasks can wake up processors in low states of sleep (a global optimization could optimize this energy use) and transfer data on long distances.