Update at 7:00 a.m. July 19: Typo fixed in the senator's last name.
Illinois Sen. Everett Dirksen is remembered for the quip, "A billion here, a billion there, pretty soon, you're talking real money." (Truth be told, it's unclear whether those were his exact words, but he's got that tagline for posterity.)
I was thinking of the former senator after listening to Microsoft's chief financial officer explain to analysts why the company intends to continue to pour hundreds of millions of dollars into a business which still isn't producing much of a return. But the online advertising business is just too important to Microsoft's future to be penny wise and pound foolish. Of course, it helps when you're the CFO of a company with tens of billions of dollars in cash and marketable securities. For more, check out the conversation I had with my CNET News colleague, Ina Fried, earlier Friday.