Why So Few Toronto Software Product Companies?

This morning, while reading a blog entry about Pulse by zutubi (via JavaBlogs), I was once again struck by the fact that there are so few software product companies in Toronto. Now, I'm not on the hunt for a job in Australia, so perhaps my perceptions are skewed, but I know a few interesting product companies in Australia even at this distance (zutubi, atlassian, etc.)

And yet, I know so very little about software product companies in Toronto; I know there are a few, but compared to the waves and waves of business / integration software jobs in the Toronto market, these opportunities are practically invisible.

Why is that? What is it about Toronto (or Canada) that seems to result in so few of these startups? Is it that a successful software product born in Toronto is likely to be purchased by a major American firm, and then vanish again? Is it that our entrepreneurs migrate elsewhere (e.g. Silicon Valley?) Do we just have so darned many of the business/integration jobs that people don't bother to start their own companies?

Don't get me wrong -- Toronto's a great place to live and work, but considering that it's software product jobs that really interest me, I just wish there were a few more to choose from.