The folks over at Eloqua analyzed data from 1500 forms over the last 3 months and found, as I expected, that the less fields asked, the less friction for submission.

Of course, not all forms serve the same purpose:

• forms offering a trial: max 8 fields
• forms offering a download: max 11 fields 
• webinar event registration forms: max 5 fields

Read the full article here

Source: Eloqua