One of the more interesting enterprise IT topics of late is the realization that there are "shadow" or "rogue" IT efforts at a vast majority of companies. These efforts are often how open source applications gain a foothold and lead to "legitimate" usage.
SOA magazine has a good overview of Shadow IT and how it relates to SOA.
The term "shadow IT" was coined for systems built without corporate approval inside business units, departments and whole subsidiaries. Born from the IT backlogs of every organization, shadow IT can drive innovation and effectiveness without hindering larger IT evolution. While organizations wrestle to centralize their applications, the reality is shadow IT is not going away. As such, it is most effective to ensure the sustainability of shadow IT instead of attempting to avoid it.Via: Joe McKendrick