Spam is pervasive across many types of electronic communication, including email, instant messaging, and social networks. To reach more users and increase financial gain, many spammers now use multiple content-sharing platforms - -including online social networks - -to disseminate spam. In this paper, we perform a joint analysis of spam in email and social networks. We use spam data from Yahoo's web-based email service and from Twitter to characterize the publishing behavior and effectiveness of spam advertised across both platforms. We show that email spammers that also advertise on Twitter tend to send more email spam than those advertising exclusively through email. Further, we use DNS lookup information to show that sending spam on both email and Twitter correlates with a significant increase in coverage: spam domains appearing on both platforms are looked up by an order of magnitude more networks than domains using just one of the two platforms.