Is there a way to validate potential lead e-mail addresses to prevent fake addresses?

One method we use with clients is to state on the reg page:  "Please complete the form below.  The asset will be sent to the email address you provide."  Then, on form submit, the lead is taken to a thank you page that reiterates that:  "Thank you for your interest.  The asset you requested has been sent to the email address you provided."  And then, of course, you must have a Smart Campaign that delivers the fulfillment email with a link to the asset.  This approach helps cut down on the number of bogus email addresses.

I second what Accelerate said. Rarely are our whitepapers used as the follow up to a form fill out. We use the thank you pages and email a link to the actual asset.

This also keeps competitors from easily accessing all your collateral.