Hi Kim,
Last i heard was that if you already had it in place, it was fine and you could use it.
If you don't have it in place, data.com's API (or something else) is no longer supported. Most likely due to Salesforce wanting to keep this an option for their own marketing cloud.
I think it is a real shame though ! 🙂 Woulld love this feature in marketo 🙂
best
Kenneth