Reporting ingame whispers

Report Spam works best (and is really intended for) illicit advertising of any kind.

Sales pitches, scam whispers, etc.

Indeed -it will put that entire account on /ignore for a period of time and immediately report it in one fell swoop.

The more people that report such chat and whispers, the faster those accounts are dealt with. They are almost invariably compromised accounts and reporting actually helps get them secured more quickly until the real player can regain control.