So I don't believe that we can direct use towards high quality print journals by providing only a small selection of high quality electronic journals. This is just my instinct, and I would love to see some data about the comparative use of print and electronic journals from a variety of situations. What bothers me most is that I'm not so sure we will all agree with each other or with our users on which journals are the quality ones. Objective measures such as the Journal Citation Reports, have some inherent flaws, one of which is that they are measures of the journal as it once was, and journals do change, for the better and for the worse. The reputation will lag behind.
Disciplines also change.
I don't believe we can predict the negative or the positive effect of our electronic purchasing decisions until we have analyzed lots of usage data. Because they were online at least two years before other major publishers, I would think that their impact factors would have risen substantially if Peter's assumptions are correct. Though it may be too soon to tell. I wouldn't be surprised if that were the case. But there may well be some positive effects of making thousands of journals electronically available to faculty.