Having noticed questions tagged as "salesforce.com", I'm wondering how the other offerings fit in on this site. I think integration questions are welcome, but what about questions solely about the other sites, such as data.com? Are questions explicitly and only about other Salesforce technologies appropriate for this site?
I think as the site grows there should be no reason why Salesforce's other offerings can't be covered also, but given that the most configurable product is Salesforce/Force.com I suspect most of the questions will fit nicely regardless.
All that aside, questions regarding Heroku should probably only be here if they involve an integration with the platform, otherwise they're akin to questions on C++ or Java and should be on Stackoverflow.com instead. Chances are, questions that don't fit will get flagged and moved to sites better suited.
If it's an integration to that site in any way, I think it's appropriate. If it's solely 3rd-party related, I think it's off-topic.
This is from the About SF -
This is a free, community driven Q&A for Salesforce administrators, implementation experts, developers and anybody in-between.
I wasn't here from the days on area51, so I don't know all the changes that got to this point though.