There has been a recent explosion in the number of applications, especially for mobile and social networking platforms. This explosion raises a plurality of performance and security issues that have to be adequately addressed. In this talk, I describe two recent projects from my group, focussing on performance in the wireless context and security in the social network context. Specifically, I will describe our work on (i) auto-configuring WLANs towards maximizing capacity, and (ii) building a distributed OSN towards providing privacy with high availability. Common to the two efforts, is the effective management of resources, either towards maximizing performance in the presence of bandwidth constraints or minimizing cost while guaranteeing both privacy and high availaibilty. Below, I provide more details with regards to the two parts of my talk. The latest commercial WLAN products that have hit the market today are based on 802.11n. 802.11n devices allow the use of channel bonding wherein, two adjacent frequency bands can be combined to form a new, wider band to facilitate high data rate transmissions. However, the use of a wider band on one link can exacerbate the interference on nearby links. Furthermore, surprisingly, CB does not always provide benefits even in interference-free settings and can degrade performance in some cases. We investigate the reasons for why this is the case via extensive experiments. Based on the lessons learned, we design, implement and evaluate ACORN, an auto-configuration framework for 802.11n WLANs. ACORN integrates the functions of user association and channel allocation, since our study reveals that they are tightly coupled when CB is used. We showcase the performance benefits of ACORN via extensive experiments. Shifting gears, we look at the acute need for privacy in OSNs. Today, OSNs are plagued with privacy concerns. While there are prior solutions towards provisioning privacy, they either impose high costs on users by using excessive resources on the cloud, or compromise the timeliness of sharing of data, by storing it on personal devices. We design and implement C-3PO, an architecture that explicitly allows users to privately share content with both minimum cost and high availability of content. Specifically, C-3PO guarantees the confidentiality of shared content both from untrusted cloud and OSN providers, and undesired users. It minimizes costs by only caching data/metadata associated with recently shared content in the cloud, while storing the rest (stale content) on user's machines. C-3PO is flexible and can be used either a basis for a stand-alone decentralized private OSN, or as an add on to existing OSNs. The latter option is especially attractive since it allows users to integrate C-3PO seamlessly, with the OSN interface they use today. We demonstrate the viability of C-3PO via extensive measurement studies on Facebook and a prototype implementation on top of Facebook.