Did you see the Times of India article on Adobe doing away with annual appraisals (TOI Article here)?
Adobe plans to do away with annual appraisals and move to continuous evaluations. While some people have said this is not possible in a larger organization, I would argue that it is very easy to do.
An excellent example of this working at enormous scale is the CBSE system of Continuous and Comprehensive Evaluation System. If the CBSE, which has 1.2 million students in Class 12, can do it so can most companies. The American education system, for several years now, has been following a continuous evaluation system rather than a once a year "final exam". With the kind of technology tools available today, it would be simple for a large well-connected organization to do monthly appraisals.
There are those who argue that short term appraisals leads to short term thinking. This is not completely true. There are ways to make short term appraisals focus on long term goals. At the same time, long term projects require short term milestones to be achieved for overall success. Even a project that is completed over 20 years needs monthly monitoring of milestones. While the goals are long term, the work required to achieve those goals is done every hour, every day.
For start-ups, monthly appraisals should be mandatory. Considering the nimbleness and pace required at a start-up, an annual appraisal seems Jurassic.