Since we've already heard from the aggressive (L)GPL side of this "debate", I think it's time for someone to provide the opposite opinion.
I write code to help users. However, as a library designer, my users are programmers just like me. Writing my Haskell libraries with restrictions like the (L)GPL means my users need to jump through hoops to use my software, and I personally find that unacceptable. Therefore, I gravitate more towards BSD3 and "beer-ware" type licenses. This also means my users aren't subjected to my religious views just because they want to use my "ones and zeros".
Also, with GHC's aggressive inlining, even if you do have a static linking exception in your (L)GPL license, it still may not hold up! Although the entire idea is untested in court, GHC can (and will!) inline potentially huge parts of statically linked libraries into your code, and this would force you to break the license terms if you were to distribute the software without source code. In Haskell-land, the GPL is the ultimate in viral licensing, and very hard to escape.
That's why I don't use (L)GPL licenses.
Just making sure both sides have a horse in this race :)
- Clark