[anigbrowl]

It's the knock-on effect. The city anticipates that in ten years, other businesses attracted by Twitter's presence will create ~3-4,000 more jobs, paying about 25% more, than if Twitter does not move in. The company is big enough for other businesses to coalesce around, whereas without them it's questionable whether enough small businesses would have the critical mass to sustain economic growth. 'We're in the same building as/next door to Twitter' sounds encouraging; 'we're the only tenant on the 13th floor of the Scary Neighborhood Tower' does not.