I just read a great blog post by John Harries at his Attainable Adventure Cruising website (one of the best, and a must read), and it succinctly sums up my exact feelings about the dangers of relying totally on modern weather forecasting and weather routers. In addition, John clearly sets out the dangers of participating in offshore cruising rallies that have in recent years lead some sailors into situations they weren't prepared for.
My one caveat on what he wrote, and I believe he would agree with, is that in the end it is the individual skipper's judgment that must determine when or if a vessel heads offshore, regardless of any professional weather routing assistance or information received. In addition, despite the pressure of a rally environment, in the end it is the individual sailor's responsibility to assess the weather, the boat's and crew's capabilities, and the schedule.
The bottom line is that the weather is still unpredictable, boats and people have their limits as to what they are prepared for and what they can endure, and what circumstances we end up in are the responsibility of the skipper and crew. It has always been thus, since before recorded history, and it will always be so.
And, here's an interesting follow-up by Ken McKinley, a professional weather router.