1. A computer-implemented method for managing capacity over-commitment in a resource provisioning environment, the method comprising: collecting historical data about capacity usage in a resource provisioning environment and failure statistics from an operational database, in addition to prior service commitments due to previously contracted service level agreements (SLAs) stored in a SLA repository; calculating equivalent capacity for the resource provisioning environment based on a defined residual benefit goal, and other business goals instrumented by way of a policy engine; determining whether placing requested virtual resources on one or more hosts is feasible, in response to determining that sufficient physical capacity is available to host the calculated equivalent capacity and taking into account anti-collocation constraints that prohibit placement of two or more virtual resources on same host, wherein the determining is repeated a number of times (N), wherein the number of times (N) is automatically computed by estimating a confidence interval for a mean of Normal distribution based on a defined significance level, and wherein the determining whether placing requested virtual resources on one or more hosts is feasible comprises checking a target risk level of resource congestion does not exceed a threshold risk probability based on determining a percentage of failures during the repeated number of (N) times; and issuing an unsafe over-commit level warning based on the determination that placing requested virtual resources on one or more hosts is not feasible.