The opposite is also true: a "negative halo effect" can be easily observed, wherein "bad" traits are also similarly grouped and feed on each other.

An interesting part of halo effects is that people seem to understand them on an instinctual level - not enough to get rid of them, but enough to exploit them...

I've drawn an extremely strong correlation in a particular online game between having a marijuana reference in one's handle and being bad at the game; being bad is not strongly linked with marijuana references, but that's only because they're in the extreme minority of the population; if you're sporting a "420", you're almost definitely underperforming. I've never bothered forming a hypothesis as to why this is, but it is.

So one day I decide to try a little experiment - for funsies, nothing rigorously scientific, just a "see what happens" thing - and predict aloud that an ally with a name referencing marijuana would perform poorly compared to the other players in the game. I turned out to be right (he was even worse than expected), but the interesting part was his response:

He implied my prediction was wrong, evidenced by that he was writing his college thesis on the effects of THC on the body.

The only way this statement makes sense is if we trace it through an expectation on his part that he can rebut the argument using the halo effect. "I am extremely accomplished academically," I could almost read on the screen, "Therefore, I am not a poor performer in this online video game."