Why bother with an alt blockchain at all when you could just sell shares/bonds which can also be traded or bought back by the issuer?  How does adding an additional layer of complexity benefit anyone, especially given how alt blockchains tend to pan out?  For that matter, why not use something like Kickstarter to raise start-up funds?

A blockchain is a standardized protocol. Shares/Bonds dont have a standard (yet). If you trade shares,
you still have to protect yourself from someone who is selling you fake shares.
And with a share being a digital currency, you could sell your shares on different websites.
As far as I can see right now it is the stock exchange like GLBSE that defines the standard of a share/bond.
And if this is the case, then the whole economy depends on wether the  GLBSE website is working or not.
And about Kickstarter, well crowdfunding is great, but this is another issue. Because
a crowdfunder doesnt invest, but rather donates. The investor wants to OWN his investment.