Just to clarify, securities issuers would simply set themselves up as a Ripple gateway. They would issue a set number of security IOUs and take Bitcoins in return. Those IOUs could then be freely traded by the market, while the issuing gateway would be free to fund their projects using the Bitcoins that were received in return for the IOUs (shares/bonds) that they issued. Dividends would simply be paid as BTC to whoever happens to hold the IOUs for the given security.
I have used Ripple as a user, although I am not familiar with the behind-the-scenes gateway, etc. stuff.
But if looks to me like this should work; if DividendRippler.com could do this with the TAABL.NET asset (
https://bitcointalk.org/index.php?topic=190193.0 ) then it should be possible to do it with more assets. DividendRippler itself might be willing to do this with more assets; I don't know (although I suppose this might risk going back to having too tempting a target for regulators if many assets are hosted by one entity). Or I imagine there is probably a way for more entities to establish themselves as Ripple gateways.
I also notice that it is apparently possible for anyone to create his own 'currency' or 'IOU's on Ripple, not just gateways. I notice for example that as a test of this feature, Bitcointalk user TTBit has created the currency DYM, which is equivalent to one pre-1965 US silver dime (
https://bitcointalk.org/index.php?topic=149533.0 ). In order to use DYM, users simply trust TTBit's Ripple address with the amount of DYM that they are willing to hold (users do not need to trust each other with the DYM, they just need to trust TTBit because all the IOU's are issued by him).... I don't know why other Ripple users couldn't do the same thing. An asset issuer should be able to make a simple webpage saying 'send me X amount of BTC per share (or send me your information if you are an existing shareholder from BTCT/LCG/BitFunder), and trust the following Ripple address for that amount of shares', and let me know your Ripple account, then will be able to send the IOU's representing shares in his asset to that Ripple address. Any user who holds these IOUs should be able to use Ripple's normal trading functions to list his IOUs for sale at whatever price he wants in whatever currency he wants; people wanting to buy shares would just need to trust the issuer's Ripple address with the number of shares they want to buy, then could buy them either from the issuer or on the open market. I'm not sure if there is a way to pay dividends this way, but at least this would be an easy way to allow people to continue to buy and sell shares during a transitional period for some of these assets that are having trouble quickly finding a new exchange to relocate to. (Although I agree that it seems that the gateway idea would provide more functionality, in particular the ability to pay dividends.)