You mean it's possible for me to issue my own currency right from the Ripple.com website? If so, how exactly would I go about it?
Yes, as soon as you have an account on ripple.com and have some Ripples in your account (you need at least a reserve of 200-300 to use all features of the system), you can do the following (substitute you/your for me/my):
1. I think up a 3-letter code for my new currency. E.g., if I want my currency code to be my initials, it would be "MPF."
2. I advertise the availability of my new currency wherever I want, together with my Ripple address and instructions for buying them. (My actual Ripple address, which you would use to get MPF units from me, is rnfLDQaxN7isxzWZuc6BM8jeiCb2WSGpdG.)
3. If you want to buy, say 1,000 units of my currency, you sign up for Ripple, get some XRP to pay transaction fees, and then grant a trust for "1000 MPF" to my Ripple address. (Feel free to try this, with my actual address above.)
4. When I receive the agreed payment (in BTC or XRP or whatever), I then send you 1,000 MPF through the Ripple.com interface. Note that these new units (which are ultimately just IOUs) get created out of thin air (they are backed by the trust you have in me). (For demonstration purposes, I hereby announce that I will send up to 100,000 MPF to anyone who grants me the requisite trust, for nothing - since this is just a demonstration for anyone who wants to try it out.)
5. People holding my MPF units can send them to each other on Ripple, and even convert MPFs to/from other currencies using Ripple's built-in currency-exchange interface, by selecting my Ripple address as the exchange for the MPF units. (This works since all MPF holders who do a trade with me as the exchange implicitly grant me a trust.)
6. Presumably, I will also allow people to sell their MPF units back to me and I will give them something back, something that is backing my units (otherwise, why would they trust the value of my units in the first place?). (For purposes of this demonstration, however, I am not promising to give anything back - however I do hereby promise never to let the number of MPFs outstanding ever be greater than 1 trillion - so they may still have some value, like Bitcoin, due to scarcity.
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Feel free to try out my new MPF currency, which I have just created by making the above announcements; it now available on Ripple at my above address. Please allow up to 24 hrs. for me to notice that you've granted me the trust and send you your free MPF currency units.