hehe. I don't think you should be discouraged, though, because:
1) You don't deal with the admissions people after you get in.
2) I have a feeling that this happens to everyone. Dragging people out just makes sense if they're borderline accept/WL or WL/reject. It's quite impersonal and driven by the law of the marketplace. If it makes sense for their numbers to do something, they're going to do it even if it discomforts the applicants. Why? Because they let you into school; they have you by the short hairs. Students can turn the tables if they have precocious numbers or are URM, and then it is schools who court the applicant.
I got my USC acceptance on my birthday, decently early for a december application, and a quick scholarship offer. I had to wait a month and a half more for Berkeley to reject me, and until mid-April for UCLA to accept me. I'm sure that's all a product of my numbers--I was a solid candidate for USC, so they were reasonably quick, Berkeley was way out of my league, so they felt no particular pressing need to get back to me soon. UCLA, with my numbers, had to be almost 100% sure I would come if admitted, so my acceptance vs. rejection or WLing was completely a process of careful yield management and class-filling. If other people hadn't withdrawn, I wouldn't have gotten in.
So in short, don't be discouraged about USC. Be disillusioned about law school admissions.
I think your point is generally correct, however USC is definitely much slower than other schools. This year their dean of admissions left, which probably contributed to their slowness. I mean, they still have A LOT pending for mid-may. At this point most other schools would have at least waitlisted a lot of the people waiting.
I do agree that if you want USC and you haven't heard yet, then all you can do is sit back and wait.