There are many ethical consideration when it comes to accounting. Let me offer a few perspective. First, accountants have a responsibility to report accurately. This might seem straightforward, but it is possible to mislead very easily. In other words through "creative" accounting methods, it is possible to lie without every lying. If you look at some of the corporate scandals of late, many of them have been due to accounting practices. Think of Sino forest.
Second, there have been blatant lying with accounting as well. If you think about Enron, WorldComm, and Lehman brothers, there were dubious actions in accounting reporting that misled the public. So, we are not talking about hypothetical situations at all. Accountants have a responsibility to investors to divulge truthfully.
Third, accountants must be careful of anything that has the potential to be a conflict of interest. This is why it is imperative to use accountants that have not vested interest in the company it is auditing.