I'm not sure what or rather Who you meant by
SE Managers
But, as far as I know, SE staff doesn't provide ads by themselves but use a third party ad provider(s).
You said
...we should be conscious of the importance of ads for the long-term
survival of SE sites(unless users directly finance SE activities).
Please note that advertising is not the only way for SE on income. as a corporate, they probably have investors and there may be many other ways for them to get big money. Also note that *Users are the backbone of the SE, and what they do, is the main reason that SE grows this big as a corporate and having the reputation on the internet. I remember someone said in a comment or in an answer, that the question on SO, How can I exit the vim editor may've earn the company a huge amount of traffic, attention and therefore money. so, yes, without users, SE is just a Q&A site on the net.
Having said above, IMHO, if we must see the ads, then,
- Ads should be workplace friendly and child friendly.
Ads shouldn't be kind of animated ads.
Ads shouldn't be kind of javascript based.
Ads shouldn't be videos and/or with sound.
Ads should be relevant to the site (AskUbuntu shouldn't get
booking.com deals)
Ads should be legit. no ads should display if it contains fake
medicine, fake cosmetics, non-FDA approved drugs, shouldn't be scams,
lottery or related categories.
Ads shouldn't redirect user to another advertiser, shouldn't force
user to go into another click-bait website.
Ads shouldn't open pop-up windows.
Ads should be legal. it may depend on the user's
location/country/state and/or regardless of the location, shouldn't
promote illegal activities, illegal drugs/medicine, black market
products, guns and ammunition etc..
Ads shouldn't be type of click-bait.
Ads shouldn't open multiple tabs and/or pop-ups on a single click
from the user.
Ads should open in a different tab/window (singular), and shouldn't
forcibly take the attention.
Ads shouldn't keep any data on user's device.
Ads shouldn't track user nor install scripts in user's browser nor
save any user data.
That's the things in my mind for the moment, if and when I get more, I'll update this.