CRM 3.0 allowed bulk edit on money fields. The multi-currency nature of CRM 4.0 removed that behavior due to concerns a business may have with the potential edits users could make. A business may not want users changing currency in bulk and a business may not want users changing money values without also considering that the records may have varying currency.
A future release of CRM should consider allowing users to bulk edit money fields provided they also specify the currency. This will be benficial for single-currency organizations. For multi-currency organizations, there should be some form of an administrative control to determine whether a user is authorized to change the currency during bulk edit.
Currently money data cleanup acitivities, e.g. zero out bad data, needs to be done through either a third party tool, unsupported database access, exhaustive manual interaction, or supported custom development.