I do not agree that this is about tithing. The preceeding text talks about the followers agreeing on owning all property together. People would help eachother and you'd get based on your needs, but you'd have to honestly give up the greed of wanting to own things.
Anaias and Sapfeira tried to take some of the money themselves and trick the others of the community.
The 'moral' of the story would be that it's not the money, and what specific troubles could come with withholding money, but the act of decieving that is the real sin.
Of course, I find it rather horrifying to actually kill (or at least use this as an illustration) people because of something like this. Surely that goes against the whole idea of Christ helping people out because they can't always act perfect.