There are a number of key threads in this forum that can give you a lot of these answers. Try these:

BitShares Forum »Development »ProtoShares »What is ProtoShares?

BitShares Forum »Development »ProtoShares »The Intrinsic Value of Protoshares (Update from Bytemaster)

BitShares Forum »Development »Keyhotee »Connecting Keyhotee and Protoshares

Ok that was the long answer. Now for some very short answers:

1. Holding ProtoShares is not holding stock in Invictus but it does give your rights to revenue streams from every DAC we release into the wild. You wind up owning shares in our DACs not shares in Invictus.
2. Each DAC has its own business model. BitShares is a family of exchanges that let you do typical trading operations on between classes of crypto assets. Our first lets you trade exposure to various common currencies.
3. Each trade has a transaction fee which is split among all BitShareholders in the form of dividends, just like any corporation splits its profits with its shareholdes. To the extent the Bitshares has value in the marketplace, you can convert your dividends into other crypto or fiat currencies.
4. Customers are anyone who would like to save or trade without leaving crypto-space and incurring various costs associated with travel between "free space" and "fiat space".
5. It will cost you a little of your stock as a fee to make a transaction and you get more stock when others pay similar fees. Value is generated inside the DAC from the services it performs which people are willing to pay some of their hard earned or purchased shares to obtain.
6. DACs are by definition crypto currencies backed by the services they perform. Even Bitcoin is a DAC performing the service of efficient money transmission.
7. Transaction fees are the profits -- for services performed of value to its customers.
8. As long as you are inside the DAC, the currency of the land is that DACs shares. The more valuable the services it performs, the more desirable it is to hold that currency in order to obtain those services.
9. Dividends are small if profits are small and large if profits are large. Each DAC publishes its distribution rules, which distribute some of the transaction fees to the shareholders (owners) and the rest to miners (workers).
10. There are several components that drive the market assessment of the expected value ProtoShares:
An assessment of the predicted value of the idea/business model of the services it will provide
An assessment of the developer(s) ability to implement the idea.
An assessment of the likelihood that the developer (or somebody else) will honor the social contract
The summation of the above expected value across all DACs currently in the pipeline.

Its up to the developers to convince the market that the above factors sum to great value. To the extent that they do convince the collective community of experts, ProtoShares will increase in value and so will each DAC according to its established value proposition in the arena of ideas.