A "work for hire" library/publisher that pays an up front commission fee to a composer becomes the owner of the copyright and typically is under no obligation to share any further sync/license fees with the composer. The composer retains their "writer's share" of the performance royalties (50% in ASCAP-speak and 100% in BMI-ese). This type of deal might be what one refers to when using the term "exclusive". This deal is exclusive forever!!
Another type of exclusive agreement would be where the library does not pay up front sync fees, allows the composer to retain their copyright, has a reversion clause and shares 50% of any upfront sync fees not including blanket licenses. This is still an exclusive deal which means you can't put the music elsewhere in a competing library for two years.
Even yet another "flavor" of exclusive is where if a piece is accepted and gets placed and/or generates a sync/license feel, the piece automatically becomes exclusive to that publisher in perpetuity, and all sync fees are still shared 50/50.
I'm sure there are more subtleties out there but the thing I'm trying to point out is that there aren't just "exclusive" and "non-exclusive" out there, those terms cover a broad spectrum of deal types.
There are benefits to both types of deals. The more I learn about this, the more I am moving towards the middle and am considering how to handle my music on a case by case basis. There may be terms that allow usage in other non-competing markets where it would make sense to take catalog that is currently non-exclusive and re-titled and place it there as the publisher under it's original title.
All that being said: Tread carefully in these waters and don't make sudden moves without fully researching the ramifications of any contracts you may be currently under. It behooves all of us to get further understanding of the inner workings of these deals so we can make better decisions and not make blanket statements like "craze" and "meaningless". It just makes us look unprofessional. We're only as good as a group as our most clueless loose cannon!! Let's raise the bar not only on our music but also on our understanding of the business we purport ourselves to be in!!

Cheers,
Mazz