Install server against MySQL
Import confluence.atlassian.com data
Try to create a space: the space is created, but you're left with a stack-trace of a primary key conflict:

java.sql.BatchUpdateException: Invalid argument value, message from server: "Duplicate entry '5' for key 1"
at com.mysql.jdbc.PreparedStatement.executeBatch(PreparedStatement.java:1404)
at net.sf.hibernate.impl.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:54)
at net.sf.hibernate.impl.BatcherImpl.executeBatch(BatcherImpl.java:122)
at net.sf.hibernate.impl.SessionImpl.executeAll(SessionImpl.java:2385)
at net.sf.hibernate.impl.SessionImpl.execute(SessionImpl.java:2335)
at net.sf.hibernate.impl.SessionImpl.flush(SessionImpl.java:2204)
at net.sf.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:61)
at org.springframework.orm.hibernate.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:339)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:302)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:174)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:196)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:135)
at $Proxy10.savePermission(Unknown Source)
at com.atlassian.confluence.spaces.DefaultSpaceManager.createSpace(DefaultSpaceManager.java:168)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.springframework.aop.framework.AopProxyUtils.invokeJoinpointUsingReflection(AopProxyUtils.java:59)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:201)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:176)
at com.atlassian.confluence.util.profiling.SpringProfilingInterceptor.invoke(SpringProfilingInterceptor.java:17)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:196)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:135)
at $Proxy12.createSpace(Unknown Source)

Try to follow that with a SnipSnap import, it also fails with PK problems:

org.springframework.orm.hibernate.HibernateSystemException: a different object with the same identifier value was already associated with the session: 3, of class: com.opensymphony.user.provider.hibernate.entity.HibernateUser; nested exception is net.sf.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: 3, of class: com.opensymphony.user.provider.hibernate.entity.HibernateUser
net.sf.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: 3, of class: com.opensymphony.user.provider.hibernate.entity.HibernateUser
at net.sf.hibernate.impl.SessionImpl.doSave(SessionImpl.java:823)
at net.sf.hibernate.impl.SessionImpl.saveWithGeneratedIdentifier(SessionImpl.java:761)
at net.sf.hibernate.impl.SessionImpl.save(SessionImpl.java:720)
at org.springframework.orm.hibernate.HibernateTemplate$7.doInHibernate(HibernateTemplate.java:299)
at org.springframework.orm.hibernate.HibernateTemplate.execute(HibernateTemplate.java:149)
at org.springframework.orm.hibernate.HibernateTemplate.save(HibernateTemplate.java:297)
at com.atlassian.confluence.user.persistence.dao.hibernate.ConfluenceUserDAO.saveUser(ConfluenceUserDAO.java:176)
at com.opensymphony.user.provider.hibernate.HibernateCredentialsProvider.create(HibernateCredentialsProvider.java:64)
at com.atlassian.confluence.user.providers.ConfluenceCredentialsProvider.create(ConfluenceCredentialsProvider.java:60)
at com.opensymphony.user.UserManager.createEntity(UserManager.java:370)
at com.opensymphony.user.UserManager.createUser(UserManager.java:242)