Snead learned a valuable lesson from Fisher...... never do what he did.
Fisher (and others) love the idea of accumulating as many picks as possible thereby reducing the risk of selecting rookies knowing you'll fail on many of them.
Snead trades up or down according to several things imo. He looks at the draft, collates that with his needs, and determines the depth in the draft of the various positions and types of players he's looking for. So if the draft is deep in WRs, and he plans on taking one of the better ones, he might move down because he knows 1 of the 2 or 3 he wants is highly likely to be there. If its a weak year for WRs and needs one, he might move up (because he knows that in a weak year you can screw up big time by looking at a player relative to the others available and not according to what his attributes need to be to be worth a certain pick in a certain round).
He also looks at what this team is going to need in a year or two, and compares that to the strengths or weaknesses in the current draft class versus next year's likely class.
Lots of moving pieces.
So just saying "move down" or "move up" must have a basis in an overall plan and the availability of players in the current year (and what they foresee as the likely candidates for the next draft as well).
