This passage reminds me of a comic I heard recently, while funny, is almost exactly what this verse is saying... the bit went something like this: "Jesus died for our sins, right? So if we don't sin, Jesus died for nothing! So I'm sinning for Jesus!" As funny as that is, and as ridiculous as it sounds, the Romans to whom Paul was writing were obviously thinking along those lines... How could you talk yourself into believing that "our sinfulness serves a good purpose"?

Romans 3:8