I'm European and I think I can answer the question:<p>1) It's in Texas, which is basically halfway around the world for Europeans. I don't think many Americans would attend a conference in St. Petersburg.<p>2) This may be big in America, but I've never heard of it, and I'm fairly tech-minded and informed.
This notion of 'where are the (mainland) Europeans?' not only occurs at SXSW but also at this website and websites like techcrunch. Where are the European web start ups? UK websites do popup now and then (Clickpass for example). Within 5 minutes of launching I knew Clickpass was alive. This never happens with Dutch websites, German websites, etc. The Netherlands for example is home to some great websites, like booking.com or joost.com (largely build in The Netherlands) and products like TomTom.com. But, there does not seem to be a startup culture over here in The Netherlands. Where do European startups meet each other? Online or offline.<p>Why didn't I went to SXSW? Too expensive, too far away.
There's a lively Barcamp Scene in Germany, practically every month one barcamp with up to 300 attendees. You can find a list of german startups here
<a href="http://www.deutsche-startups.de/a-z/startups-a-z/" rel="nofollow">http://www.deutsche-startups.de/a-z/startups-a-z/</a>