I believe, ever since they put in the rookie salary cap, there has been a big number of draft day trades on the 1st round...
Here is link to 2012 draft info: http://en.wikipedia.org/wiki/2012_NFL_Draft
There were 7 trades for 1st round swaps on Day 1.
Similarly, there were 5 trades in the 1st round on Day 1 in 2011 (Which was the first year of the Rookie Salary Cap).
This will be a trend and I expect there will be a similar # of draft day trades on day 1.