If you are playing Daily Casts in your Criminal Deck right now, consider giving Tapwrm a try instead. Tapwrm can earn you much more in credits than Daily Casts, and it puts pressure on the Corp to either keep its credit count low or spend time purging. It also has a lower up-front cost than Daily Casts.

This card is most effective when you are not running lots of other virus cards. When the Corp's decision about purging is just to eliminate this card, it becomes much more difficult to justify.

I've yet to see a corp manually purge once I've played a Sac Con to support this. 6 clicks to prevent the runner from gaining 1-2 credits a turn (typically) is just not appealing. —

Mentioned in some comments, but put here to give it more visibility.

So here is a play that is explained in the FAQ for combo lovers.

Have Team Sponsorship on table, 1 copy of Research Grant never-advanced on board, and 2 copies of Research Grant in HQ.

Score Research Grant. Trigger Team Sponsorship to install copy of Research Grant. Score that copy of Research Grant off of triggered ability on first copy scored. Trigger Team Sponsorship to install third copy of Research Grant. Score that copy off of triggered ability of second copy scored.

4 cards, 3 clicks (+2 to install TS and first agenda), 3 credits to score 3 points.

A strong card in a meta where runners pack single copies of breakers and rely on pulling things out of their heap at key moments.

The most challenging thing about using this card is deciding when to pull the trigger and what to target. It is often better to use it early to hamper a runner than to clog your hand holding it and waiting for the stars to align for the perfect play that wins the game.

Levy-hunter! So many people rely on an installed Same Old Thing to use it. —

For four credits, you are not getting a lot of utility out of this card. Yes, if your opponent has only one copy of a certain breaker, then sending it to the bottom of his stack could be useful, but then you are still spending four credits and precious card slots on a card that does not have a big impact on the game.

Since the run has to be successful for the effect to go off, you cannot afford to put it in a server with an agenda. It is best used on the centrals or as never advance bait in a scoring server that might create a window for you to score in your next turn as your opponent searches for his lost breaker.

You can use it along with Ash in a scoring server. This way if the Runner prefers to ignore the trace and try again, he'll lose one of his breakers, which can be quite problematic. —
And if you have it in a server with Ash, you might be playing HB, which runs Breaker Bay Grid and suddenly Will-o'-the-Wisp is complete BS. —
And since Will-o'-the-Wisp is not unique, it can't be turned off by the Rumor Mill and you can have a couple of them in one server, resulting in tons of frustration from the Runner, that has to dig out half of his rig from the stack. And yes, it's ridiculous if you have Breaker Bay Grid installed. —
I think we will see this card more often - now that Stealth is rising in power and Rumor Mill annoy glacier builds. —