What risks are there if we enable read committed snapshot in sql-server?
Summary


If you have locking problems then you have a problem with your code: it isn't the database engine
It isn't a magic bullet
You may add more problems


Load

It will also increase load on your tempdb and CPU. Also see: 


"Performance Impact: The Potential Cost of Read_Committed_Snapshot" (Linchi Shea)


Safety

Most important, snapshot isolations are not safe in many cases by default. Read "Snapshot isolation" (Wikipedia) for more on write-skew anomalies. The next section is "Making Snapshot Isolation Serializable" to get around this.


  In general, therefore, snapshot isolation puts some of the problem of maintaining non-trivial constraints onto the user, who may not appreciate either the potential pitfalls or the possible solutions. The upside to this transfer is better performance.


Also see:


"The Potential Dangers of the Read Committed Snapshot Isolation Level" (JimMcLeod, disputed in comments by Alex Kuznetsov)
Deadlocked!: "read committed snapshot" Explained (Nick Berardi)
Serializable vs. Snapshot Isolation Level, the Marble problem (Craig Freedman)
Reads involving UDFs under READ_COMMITTED_SNAPSHOT may seem inconsistent (Alex Kuznetsov)