I've read an interesting take on this matter, months ago, but I cannot pinpoint it right now off my memory. It goes more or less like this: the jewish DIETARY command regarding blood is covered by the command 'abstain from strangled meat'. However, the command 'abstain from blood' would encompass everything that, under Moses' law, would make someone carry blood guilt, such as intentional murder, or homicide by negligence. There was some pretty convincing scriptural support given, which I don't recall at the moment, but my recolection was that this is the argument that makes more logical sense.
I would also add another possibility, that happens to possibly merge with the above. The Israelite married males were sternly warned to avoid sex with their wives during their menstrual period. In Jesus' day, one of the reasons the Jews avoided defilement by association with gentiles was because the gentiles kept sexual intercourse with women during their menstrual period. This was a serious issue under Moses' law. I propose it would also be a cause of tension between Jewish Christians and Gentile Christians. So, the quite generic command to 'abstain from blood' could be a diplomatic way to address a very delicate and intimate issue of sexual conduct.
Eden