I guess it was inevitable (maybe even overdue?) that data.com would head into the duplicate management business.
With Winter 15, you will have the ability to use Data.com to do inline blocking and alerting of duplicate records. This is more of what tools like DupeBlocker have done for us in the past, but still isn’t the bulk clean-up of duplicates like what you’d use DemandTools for. From the release notes it’s not clear how “fuzzy” the matching can be. With some tools – like CRMFusion’s – you can include fuzzy matching logic that does matching like knowing Jim is short for James as a first name, or knowing GearsCRM and GearsCRM, Inc. are the same even though it’s not an exact match. It does look like you have the ability to create matching rules to determine what you consider a match and that you can create multiple rule sets. For this first roll-out, looks like it only works on Accounts, Contacts and Leads and that it will not look across objects (can’t block a duplicate Lead if a Contact exists). In addition, the Quick Create ignores the blocker – shocker there. Quick Create is like the bane of every admin’s existence! (surprised there isn’t a meme cursing Quick Create out there already – and yes, I looked) Finally, just a warning, for Winter 15 this is a beta feature and this one has a direct impact on your data and users, so play with this one a bit before turning it on in production. One other thing that I’d recommend here is before turning this on, double check how this works with AppExchange products that you have hooked up. I could see tools like Marketo, Hubspot, etc. choking on this. Might be fine, but be careful. - See more at: http://gearscrm.com/salesforce-winter-15-new-features-part-1#sthash.UFMDsLXG.dpuf
You can set Duplicate Rules for certain objects