JSP consumes extra hard drive space and extra memory space.
For every 30K JSP file on the server there must be a 
corresponding larger-than-30K class file created. This 
essentially doubles the hard drive requirements to store JSP
pages. Considering how easily a JSP file can <%@ 
include> a large data file for display, this becomes a 
real concern. Also, each JSP's class file data must be 
loaded into the server's memory, meaning the server may 
eventually store the entire JSP document tree in memory. A 
few JVMs have the ability to remove class file data from 
memory; however, the programmer generally has no control 
over the rules for reclaiming and for large sites the 
reclaiming probably won't be aggressive enough.

JSP requires a compiler be shipped with the webserver. 
That's problematic, especially since Sun doesn't give away 
the tools.jar library containing their javac compiler. Web 
servers can package an outside vendor's compiler such as 
IBM's jikes; however such compilers generally don't work on 
all platforms and (being written in C++) aren't much help to
 a pure-Java web server.