All Commercial products offers solution as larger aspect of enterprise that’s where it is critical for  Architect/solution developer to understand the nitty gritty of out of box module in relation with business requirement. You would fins many helpful posting regarding reverse replication .

http://helpx.adobe.com/experience-manager/kb/HowToUseReverseReplication.html
http://www.cqtutorial.com/courses/cq-admin/cq-admin-lessons/configure-cq-replication/cq-reverse-replication
http://docs.adobe.com/docs/en/cq/current/deploying/replication.html#Replicating%20from%20Publish%20to%20Author
This is one of the most comprehensive one http://www.wemblog.com/2011/10/how-to-set-up-usergroupprofile-reverse.html

You need to ask a question why you need Reverse Replication , Please verify your requirements on this?

1. User profiles needed to be reverse replicated because has some user preference data, Does that moderation needed on author side?
2. Is it anonymous data ?
3. How many Publish you have in your setup? is it Non-Cluster setup or clustered setup amongst publish?
4. what’s volume of content in typical working hours (>10000 or <10000).

Let us come on Solution now

Solution 1.

If your publish is non-cluster and you think user generated node might go more than 10000 in a days, hold your hand and this is going to cause trouble for you, you need to use restful Service and store user generated data on one location. You can have separate Solr Data repository or have one additional publish  server and use that only for user data repository + service. Don’t go on reverse replication path out of box of AEM/CQ5.

Solution 2.

If Publish are clustered , Even more than 10000 user generated data would not be a issue.

Reverse replication can be implemented in couple of way

1. Enable outbox on publish
2.Enable Reverse replication agent on Author to poll user generated content so that it could retrieve data.
3. Create or use out of box activate workflow through Workflow Launcher as soon as new content is available on auhtor to push it across other publish in network