Using, or perhaps misusing, prototyping can also have disadvantages.
Insufficient analysis: The focus on a limited prototype can distract
developers from properly analyzing the complete project. This can lead to
overlooking better solutions, preparation of incomplete specifications or the
conversion of limited prototypes into poorly engineered final projects that are
hard to maintain. Further, since a prototype is limited in functionality it may
not scale well if the prototype is used as the basis of a final deliverable,
which may not be noticed if developers are too focused on building a prototype
as a model.
User confusion of prototype and finished system: Users can begin to
think that a prototype, intended to be thrown away, is actually a final system
that merely needs to be finished or polished. (They are, for example, often
unaware of the effort needed to add error-checking and security features which a
prototype may not have.) This can lead them to expect the prototype to
accurately model the performance of the final system when this is not the intent
of the developers. Users can also become attached to features that were included
in a prototype for consideration and then removed from the specification for a
final system. If users are able to require all proposed features be included in
the final system this can lead to feature creep.
Developer attachment to prototype: Developers can also become attached
to prototypes they have spent a great deal of effort producing; this can lead to
problems like attempting to convert a limited prototype into a final system when
it does not have an appropriate underlying architecture. (This may suggest that
throwaway prototyping, rather than evolutionary prototyping, should be used.)
Excessive development time of the prototype: A key property to
prototyping is the fact that it is supposed to be done quickly. If the
developers lose sight of this fact, they very well may try to develop a
prototype that is too complex. When the prototype is thrown away the precisely
developed requirements that it provides may not yield a sufficient increase in
productivity to make up for the time spent developing the prototype. Users can
become stuck in debates over details of the prototype, holding up the
development team and delaying the final product.
Expense of implementing prototyping: the start up costs for building a
development team focused on prototyping may be high. Many companies have
development methodologies in place, and changing them can mean retraining,
retooling, or both. Many companies tend to just jump into the prototyping
without bothering to retrain their workers as much as they should.
A common problem with adopting prototyping technology is high
expectations for productivity with insufficient effort behind the learning
curve. In addition to training for the use of a prototyping technique, there
is an often overlooked need for developing corporate and project specific
underlying structure to support the technology. When this underlying
structure is omitted, lower productivity can often result.