In 2009 rents dropped rapidly in Mountain View. I moved here in early '09 and my employer paid a realtor to show me around for a day. Told him my budget was $2000/month, and asked about a fairly swanky mostly-corporate-housing-but-a-few-individual-tenants complex. "Oh, that one's out of your price range", he said.
Ended up taking an apartment there for $1400/month six months later, and it stayed at that level for 3 years. (And then shot up rapidly afterwards - I left when it hit $2400/month 5 years later, and it's currently renting for $2900/month.) It had gone down so rapidly that its price was underneath the less-swanky complex a block down the street which normally rented for ~$300/month less and had itself cut rents from about $1800/month to $1450/month over those 6 months.
Rents are sticky - landlords try to avoid cutting if they don't have to. But when there's a choice between letting the apartments go vacant and servicing your debt payments, they have to cut, and if there's a shortage of tenants at that time (because everybody's left and gone home) the cuts can be pretty drastic.