Ajoys, I doubt that an agent cares who pays the commission, as long as it's paid.

Commissions are down to 4.5% in CA now? Wow, is the market in places that bad where agents are scrambling for listings or is there just too much competition in the field so agents are lowering their rates?
I think the main problems with FSBOs anywhere, not just in CA are:
1. Sellers don't/can't expose their property to the greatest number of potential buyers. The MLS is a great tool, but I don't know if it is flat fee to list on it or if it is a percentage of the final price.
2. A lot of sellers doing FSBO don't realize that savvy buyers expect to save at least 1/2 of that real estate commission that the seller isn't paying. People looking at FSBOs rather than through agents tend to be locals, or at the very least extremely familiar with prices in an area.
3. People are too timid to do their own negotiating and feel more comfortable using an agent, and/or they have problems with for example financing that agents can help with because of their network of contacts in the mortgage field (and their potential for repeat referrals the other way). Also, with all the mandatory disclosures now, an agent is just one more person you can sue in the lawsuit chain.... I think this last statement is especially true in CA.
As soon as the sign goes up any FSBO seller will always get calls from agents saying they want to list the property or they have a buyer right now (yeah, so they can get a look at the property themselves to perhaps lowball you). There is nothing to prevent a seller saying "No, I won't pay a commission, but I can pay a finder's fee (anywhere from $200-$1000 depending) because I will be using my own contract for the sale." Some people just don't want to work with agents in the normal relationship, or any relationship.
If a house is in a desirable area, and the price is right (price is usually wrong if a house sits for six months) for the house, FSBOs can sell just as easily as agent-represented houses. In CA, even FSBO's aren't exempt from disclosures and the usual septic/roof cert, etc., correct?
Also, there is a book out by Bill Effros called How to Sell Your Home in 5 Days, where you basically have one open house walkthrough scheduled in the local paper, and then have bidding sessions. Might work for some people. The book is a very quick read, and might be at your library.