Ok, I realize I might have given the wrong impression here. Sorry.
So here's what we are doing: by artificially inserting ASes into the AS-set of an announcement, the ISP that makes the announcement can control where the announcement is propagated and thus discover paths followed by its announcements that are not usually visible, giving it a more complete knowledge of network topology in the vicinity.
Please just clarify the following point: do you intend to advertise paths containing AS numbers belonging to other entities on the public Internet without the permission of the owners of those AS numbers? You admit that you don't know what the consequences of this injection will be. It seems to me that there are enough issues with this type of experimentation *with* the permission of the AS numbers you plan to use. But the ethical issues with using them without such permission seems to me to be insurmountable. DS