The biggest problem is it's image - it's full of large stuffy software / tech companies that cater to business and not the end consumer. These types of businesses are not likely to attract young hackers that will truly innovate. I get the feeling that (for the most part) route 128 is where good hackers go to settle down and live a "normal" life.
Another reason 128 doesn't attract the hacker crowd is the availability of public transportation. Its a pain in the ass to get to any of the major office parks / buildings out there without catching multiple busses or trains. Most young innovators don't have the desire or the money to pay for a car in Boston which is necessary to make it to the area.
So - fix public transportation first, and maybe some startups will decide to make a home out there. Hopefully that can slowly build the hacker brand east coast style :)