Bay Area home sales continued their downward slide in May, with fewer properties changing hands and the mix of sales tilting toward higher-priced houses.

In the nine-county area, 5,487 existing single-family homes were sold in May, down 17.4 percent from May 2006, according to DataQuick Information Systems. The median price rose 5.9 percent to $720,000.

Looking at both new and resale homes and condos, sales volume was down 18.7 percent to 8,080 transactions, while the median price was up 3.4 percent to $660,000.

“Sales are really low; you’d have to set the clock back 12 years to find another May with lower sales,” said Andrew LePage, an analyst with DataQuick.

I did not get in on the ground floor of Google. I did not grab 50,000 shares of Flickr before it was bought for $8 bazillion by Yahoo, thus instantly affording me a fleet of new diamond-encrusted Aston Martins and a set of solid-gold teeth.

I do currently own a nice fistful of Apple stock, which I bought at 17 (!) and which is now worth a small carload of iPhones, but in this ridiculous and demeaning and utterly depressing San Francisco housing market, this equates to enough money to buy roughly 9 square feet of a former meth lab in an industrial loft in the Outer Mission.

“Is overbidding still common?” queried a recent poster on the Craigslist housing forum. “We are looking in Piedmont, CA and the agents are always pressuring us to overbid!”

The perplexed home buyer got a rash of responses, from “Do Not overbid — it’s just money down the drain!” to recommendations to follow their agent’s advice. Given the new market, this is a tricky one. Last month, I faced the same question from a friend who had fallen in love with a four-bedroom house in Kensington listed at around $750,000. “My real estate agent told me they were expecting 10 offers and so we should bid at least $850,000,” my friend told me incredulously. “Is that really how things are nowadays?”