If you've forgotten what a true deep threat receiver looks like, pull up footage of Jerry Rice's early years in the NFL, back when he averaged a ridiculous 18.4 yards per reception from 1985 to 1989.
Jerry Rice Highlights (via 49erLegends)
Now I like the current crop of receivers the 49ers have signed right now, namely Mario Manningham, Michael Crabtree, and Anquan Boldin, but these are all 6'0 possession receivers averaging around 13 yards per reception. Although they're physical guys with good hands, they aren't the fastest yards-after-catch (YAC) guys nor do they have the height to elevate over taller defensive backs.
Vernon Davis is the closest thing to a deep threat that the 49ers currently have, but he's a tight end and is frequently asked to block. Is there anyone else in free agency or in the draft you think the 49ers should pursue to fill this critical role?