It is beginning to look like all the large companies that were hiring to deny talent to competitors are now feeling comfortable trimming the fat because they know that the startup fundraising scene has shifted dramatically in their favor (fewer potential competitors being funded), and they can trim costs and regain the initiative as far as having more leverage/bargaining power over current and future employees is concerned.
My theory is that it's cyclical: trim costs today, and a few years from now buy up all the startups that resulted from a suddenly flooded tech labor market. Rinse and repeat.