clive illustrates one of the reasons it's difficult to get a name actor to commit to an unfinanced movie. If the movie they attach themselves to doesn't get made, for any variety of reasons, it can look bad on the actor. If their "name" fails to bring in financing, the name value drops.
I completely agree -- the only way to get this to work is to understand the actor's perspective -- and not throwing their name about to promote the film before you've secured finance is part of that (when I attached my name, those long term member on this forum will remember that I never even hinted at who she might be -- protecting her reputation was top of my list -- as it stands today only four people in the world, including her, ever knew she was attached to the project -- which means even though the project folded, I can still go back to her)
However, one of the factors that works in a film maker's favour is that it's possible to be a "name" and still not to have had serious work for the last two years (or longer).
Names fall out of favour and even though they are still earning from previous projects, they may not currently have any offers on the table.
Where this is particularly true is with TV names, whose high profile series got canned three to four years ago.
For TV actors the transition to film is often worth something more than payment up front, providing it jump starts their flagging careers.
These kinds of people will take often take on indie projects, as a way of reinventing themselves, especially if they think the film will be Sundance fodder. But, as I said before it's all down to the script.
The flip side of this is that appearing in a "piss poor, low budget, genre film" can pretty much destroy an actor's career.
Selling yourself as a viable project is therefore about having a great script, having a great showreel and having the kind of marketing plan for the film that will benefit the actor's profile.
Mainly though, it's the script -- pretty much every actor out there is looking for a good script -- and the reason that's so important is because they are so very, very rare.