Some investment banks seeking to be added as underwriters to Snapchat owner Snap Inc's initial public offering registration document have been denied access to review it before it is made public this week, according to people familiar with the matter. The unusual move underscores Snap's relentless campaign to crack down on information leaks. For Wall Street banks, it pits their desire to appear on the front cover of this year's most high-profile IPO against their reluctance to have their names featured in a regulatory document they have not seen.