Update: While there are no plans to productize this feature, all Marketo customers can chat with the other Marketo users in their company in their secret group in Community. Every customer has a secret group.
Correction: To find your secret group either search your company name and it will populate, OR, if you have not been invited yet, contact your company's Marketo admin to be invited.
Please contact your company admin and they can invite you! Let me know if you have issues. Also, thanks for bringing this up because I was not clear. Since it's a secret group I should have mentioned, if you are not a part of the group it will not come up in search. If you are a member it will come up in search.