You could also argue the opposite: Having a job this week is no indication that you will have a job next week, and that without a specific contract with a specific term in it (good luck), the "at will" clause in your contract or state law means that you should always plan to be laid off at any time and have a few months of savings on hand.
Hmm... I think people have misinterpreted what you said. It seems to me to be prudent advice (of course, I've been in companies going through layoffs more than once).
Despite best efforts on everybody's part, sometimes (I might be tempted to say "often" wrt startups) your job dries up. Even if it's obvious that the company was in trouble when you look back, for a variety of reasons you are never going to be given any kind of notice that things are not going to continue as they were.
Sometimes companies are very forward thinking and plan well. In that case they let you go while there is still money left to pay a severence. Sometimes they grind the company into the dust and there just isn't anything left. Often the business people are hoping beyond hope for a miracle to happen and when it doesn't there isn't any money that can be earmarked for severance. As pointed out, the law allows companies a fair amount of leeway here.
Don't leave it up to your employer to look after you. Make a plan. What am I going to do if I loose my job tomorrow? Make sure it is a viable plan. If it isn't, do what ever you need to do to make it viable as soon as possible.
