Former EMC responding to the original poster: I've been laid off 4 times in my career, all of them at startups that either closed or had bad quarters.
I've also worked at big companies like EMC and Netapp. Never got laid off in big companies but I did go thru layoff periods and saw very good people let go.
From my experience in the tech field, I cannot assume that I will work for a company until retirement. I will probably get laid off sometime in the future.
It's YOUR responsibility to prepare yourself. You have to have the mindset that I can be laid off tomorrow and thus, need to prepare myself for it.
Keep your skills fresh. If what you are doing at work is not fresh, then spend your free time learning new technologies or skills.
Save 6 to 12 months salary.
Keep networking even when you aren't looking for a job. Keep in touch with former coworkers, meet them for lunch, inquire about any hirings in their companies, even if you have no interest in changing jobs.
Go to job interviews even though you have no interest in working for that company, just to get practice on job interviews.
That's how I got prepared.