Dow Jones has revealed the real reason for the MarketWatch purchase: the financial site was bought to ease a potential ad inventory crunch. The company spent six times MarketWatch’s 2004 revenue to be sure it gets some of the U.S.$10 billion online advertising spending.

In Canada, online advertising revenue has grown almost 68 per cent since 2002, but still amounts to less than $300 million, or about 1.5 per cent of the overall advertising market. (Online ads in the United States account for about 3.7 percent.) But don’t let those figures distract you. Many sites here are facing inventory crunches — we’ve spent the last month at The Globe and Mail opening up new, or enlarging existing, ad slots to meet demand — and advertisers’ spending may yet spark another content boom.

Let’s hope, though, it’ll be a lot more stable than the last one.