Well, saying that there is no warning is disingenuous. There’s at least the dialogue box that pops up warning of a trig invasion (unless you suppressed it), and the route planner shows a special icon for a lowered security status.
Should CCP give more warning? Maybe. But then again, I’ve never accidentally jumped into a final liminality system. Thus, I’m wondering if the problem is that CCP isn’t giving enough warning, or if some players just aren’t paying enough attention.
Oh, and you might be interested in this thread.