The fact is, that since the Pats traded a first rounder in 07 for a first rounder in 08, it wasn't a fair trade to begin with. Deferred compensation needs to be devalued by one round. But since SF is doing so badly, trading a 20 something pick for a top 10 pick the following year is actually more along the lines of a favorable trade.
Also, remember that the Pats traded their 2nd #1 because they had an extra for Deion Branch. Another case of deferred compensation - this time a player for a pick the next year. Waiving that piece of paper around during the AFCCG doesn't really help Alexander cover Clark any better does it?
In theory once you get the ball rolling - always have 2 #1s and always trade the latter of them for a #1 the following year - you get two chances to get a great pick and then defer the other pick for two chances the following year. This brilliant scheme is hard to get going again without the lead domino (i.e. Drew Bledsoe, Deion Branch).