Oh man it's a long story. I'm 29 now and when I was in my teens I remember the glory days. My dad's small business had season tickets and I got to go along to 10-15 games a season. I even got to go to one or two of these games:
http://en.wikipedia.org/wiki/1990_NBA_Finals with my dad. Rip City, as cheesey as it was, was hard not to get into.
These are memories that are still crystal clear in my head, that I still get excited thinking about. These are the reasons that no matter how bad the franchise is, I can't stay away.
I had a whole long post written but what it comes down to is that Allen and Whittsit tried to rebuild without rebuilding. Instead of re-tooling through the draft they tried to re-tool through trades, remember 'Trader Bob' Whittsit? I don't think for a quite a period there, that the team had a top ten draft pick. Consecutive playoff streaks are nice, but they really hamper a rebuilding job. And as the risky players eventually backfired, as they usually eventually do, people just got turned off. Paul Allen's aloofishness (is that a word?) also turns people in this city off. He could do a lot towards goodwill if he'd come out publicly and say...something but he's real hermit-ish. But to be honest, Portland is a city full of trend-freaks and front-runners anyway, so it's easy to see why nobody goes to games anymore. Once the team is good again, they'll be back I promise. People would be there this year, but we're all sort of suffering from battered wife syndrome and we're afraid to trust again. If there are no more crazy implosions, attendance will go up next year - especially if the team has a good draft.