How to cancel hard disk from wanting to format and how to get my files back?
This question is tagged [data] but you know it's about [data] from the [hard-drive-recovery] tag.

Best Light Software to Manage Large Amounts of Data?
This question is tagged both [database] and [data], but [database] inherits [data], right?

How to quicky connect to a sqlite database with OpenOffice.org Base?
This question is tagged [data], but shouldn't it be tagged [database] instead?

[data]
Shows some more issues of tags that are actually multiple words and might need a hyphen:

• Should [free] + [data] be [free-data] or just [free]?
• Should [data] + [query] be [data-query] or just [query]?
• Should [data] + [validation] be [data-validation] or just [validation]?
• Should [data] + [file] be [file-data] or [data-file] or [file] or maybe nothing or something else?
• ...