Oracle has improved cursor_sharing several times over the years. Remember, adaptive cursor sharing is only deployed in rare cases where a skewed column distribution (as noted by the histogram) indicates that a different execution plan would be faster. For example, a query with a popular bind variable value would be best served with a full table scan while an unpopular bind variable value would benefit from an index access plan.
But remember, this is a rare occurrence in many systems.
Based on extensive experience in the industry, it appears that about 80% of shops have uniformly distributed data. Large tables remain large, and the distribution of values within a column remain unchanged.
On the other hand, roughly 20% of databases experience highly volatile data loads, where tables are small on one day and huge the next, or cases where there is a "difference that makes a difference". In these databases, huge changes in the tables data (usually associated with high DML) changes the distribution of data values, necessitating a re-analysis of column histograms.
Read more about 11g adaptive cursor sharing:
http://oracle-tips.c.topica.com/maamW0iabO3zjbLGJrib/
Inside Adaptive Cursor Sharing
