I'll start from an arts angle.
I really like music, and one of the main reasons I live in Portland is the incredible music scene. Coming from San Francisco, one can see a million reasons why so many bands (and artists) move from SF/Oakland to here. A million more houses with basements, let alone dwellings that don't share two sides with others. (in SF, even practice spaces are hard to get, even when you're able to afford one).
And of course the cost of living is better than SF, so theoretically artists can spend more time on their art.
But then you notice a lot more "community" resources in Portland, too, like the IPRC for zinesters. (free/very low cost access to old-school letterpress, Macs w/layout apps).
And MANY small venues for bands to play/artists to have shows, including many all ages venues, sometimes co-ops, sometimes regular business, sometimes house shows (but houses that have "real" names, and a decent setup, and show schedule) (high turnover, but these places are always starting up).
The venues are a really important building block for artists. Sometimes they're coffee shops with 20 feet of wall space for photos, sometimes they're spacious warehouses for orchestra bands.
But they are not just a satellite for OTHER artists, these spaces are somebody's dream in their own right. I now see restaurants and cafes in Portland as their own kind of awesome art/startup business that I've never seen anywhere else.
A dungeon-like donut shop? Vegan convenience store (they don't even try to be healthy :D), An all food-cart food court?
For whatever reason, people try crazy business/art ideas all the time in Portland, probably because failure isn't that terrifying financially.
But it's not just the "low cost" that I give credit to in Portland, but the symbiotic nature of businesses and projects. It's probably fragile, but all these disparate pieces are critical parts of other peoples projects. It's not mere generosity or community spirit, but just the nature of the ecosystem that gets created when you have enough people with a sincere passion in different parts of a common theme.
Some of the traditional building blocks of tech startups are missing in Portland (VC, multiple universities with business friendly tech research), but I think one reason that Portland geeks are unphased by this is that we're so grounded in some of the DIY principles of punk (there, i said it), that resourcefulness/open source/small scale scrappiness are just "business words" for values we've already internalized.