If there is confidential information the user can obscure this, the point is the important part is the exact format/wording of the error message, and the error code(s) if applicable.
If the user does not want to post the information publicly / wishes to send it privately, it would probably be a better idea to deal with Tech Support directly, rather than risk getting misleading/incorrect diagnoses from other users here due to lack of information.
Re: voluminous logs - generally most users would post the specific message/error they are concerned about; sometimes further logs are required to get a better picture, even so, unless the entire log is posted it's generally not that much of an issue. The idea is to provide relevant details up front so the problem can be resolved faster.
In terms of "inundating the forums unwantedly" - I wouldn't regard having complete messages (even if verbose) as unwanted, particularly if it helped to resolve an issue; unwanted inundation would be more along the lines of unhelpful suggestions that demonstrate material lack of understanding, such as your comment(s) above.
