Advantages of anynomous events.

[chriseth]

Fixes #6785

[guylando]

@chriseth

1. when you say that they are cheaper to deploy and call, is that by a significant margin? is it worth the loss of ability of searching the event by name?
2. if such events are used then how will it be possible to analyze those events data if there is more than one anonymous event? by the parameters?
3. maybe it could be recommended to always make one of the events anonymous and then it will be easy to distinguish the logs emmited by it compared to the named events?

For me personally it is still unclear when to consider changing an event to be anonymous and how to be able to analyze this event logs.
I don't think I saw anonymous events anywhere in OpenZeppelin contracts or anywhere else. So maybe other people don't fully understand those aspects too.

[chriseth]

@guylando the gas costs always vary. It also depends on whether deploy-time cost is more valuable to you or whether run-time gas is more important.

Nobody said anonymous events are very useful. I would say the documentation contains all the facts, but it should not draw any conclusions if the conclusions are not easy to draw. If you only have a single event in your contract, then it probably makes sense to make it anonymous.

[guylando]

That is a great use case, thanks