What would an agent regard as a good rate for e-rights?

Hi,

Does anyone know what a writer should expect his/her agent to look for in a publishing contract regarding electronic rights? The ballpark industry standards regarding a writers cut for hardpack and paperback are easy enough to find, but the digital rights part seems confused to say the least.
Would be grateful for any guidance,
Thanks.

[Not fully sure if this belongs here or in E-Publishing]

I'm talking about a contract from a regular traditional publisher. I understand these contracts generally contain a clause about future electronic rights.

Thanks for the info. I worry that any who lock themselves into these percentages now will lose out if there is a major overhaul of them later on.

We really need agents to be on the ball about it, but as you say, its a changing landscape so very hard to define. E-book sales via Amazon or the, about to be launched, "Google Editions" will accelerate dramatically over the coming years.

Thanks again.