20/20 hindsight is a wonderful thing. Evo explained the background very succinctly, but to expand a little... it's just a tad disingenuous to suggest that "they" should of thought of security at the time. It was difficult enough just getting all those different brands of computers and operating systems to talk to each other in the first place, let alone devising ways to stop them...
This is a little difficult to imagine if you've been brought up in a world that only knows of Pee Cees running Micro$oft...
Solutions? There isn't an easy one. Best bet may be to build a whole new system from the ground up and roll it out in some way. Backwards compatibility is probably the wrong idea, but it makes the migration of millions of non-technical users to "Internet v2.0" a huge problem. Make it backwards compatible and you leave the prospect of all the old holes. It's a problem for someone smarter than me
Call me cynical, but I wouldn't be at all suprised to discover that Bill hasn't secretly embedding the "Micro$oft Secure Mail Application" inside Windoze products for years. One day, he'll announce that he has the "answer" to spam, switches it on, and everybody (who uses Micro$oft) is "protected." Oh, forgot to mention that if you
don't use Micro$oft, you won't be able to read
any email from the MSMA using any non-M$ mail client. And you have to trust M$ to be the final arbiter of what constitutes spam then... Of coure, I'm probably being excessivley cynical...