I recently gave a talk about my experience earning to give, and someone asked whether I saw the direct impact of my work as positive or negative. This is a good question, and a common objection to earning to give: you wouldn't want to take a job that was majorly negative for the world in order to earn a bit more money to donate. So how is the world different with me doing this job as opposed to something else?
So one question, then, is whether the display ads business is overall positive or negative for the world. I think it's generally positive, despite some downsides: the majority of websites are funded through ads, and this has allowed an enormous diversity of information to flourish. I can afford to write for fun and run this site without ads on it , but many people with interesting things to say can't. The New York Times can convince some people to pay, but a subscription-only web would be much worse. Overall, ads are a very progressive and democratic way of funding things: everyone can read and everyone can write, not just people who can pay.
On the other hand, it's not ideal. Ads are often annoying, and can get in the way of what you're trying to read. They can be slow to download or execute and delay the rest of the page. Similarly, they can download large images or videos using up your metered data plan. While sometimes ads fill a beneficial function of informing you about something you'll honestly be better off from having purchased, other times they're trying to convince you to spend your money foolishly.
Many people would put ad tracking on this list of downsides: sites pass information to data brokers that build custom profiles for each user and allow personalizing ads. From my perspective, however, while having this information collected seems a bit creepy, it allows showing ads I'm more likely to be interested in. This makes publishers more money than showing untargeted ads, and I'd much rather fund them through better ad targeting (invisibly intrusive) than through more obnoxious ads (visibly intrusive).
On balance, it seems to me like the display ads business is positive, though there are ways to make it better.
My main project these days is an attempt at that, via making ads be declarative. The most well known example of a declarative environment is CSS: you give a lot of rules for how you would like your site to be displayed, and the browser makes that happen. I'm helping build something where ads will work the same way, specifying what they want to do instead of directly executing code to make that happen.
When ads do directly execute code there are a bunch of problems:
- It can slow the rest of the page down, sometimes to the point of being completely unresponsive, since the web is single-threaded.
- There's a lot of duplicate work, since all the different people involved in creating and serving the ad are trying to measure things like whether the ad ended up on screen.
This doesn't solve all the problems with ads (you can still make annoying ads that cover content or move around) but it does improve some aspects.
Determining what effect on the ads business my work actually has is very hard, but I think both the overall business and my specific work are positive. It's not beneficial enough that I see "work on display ads" as potentially one of the most beneficial things someone could do with their career, and I don't count it at all towards my altruistic impact, but I also don't think of it as a harm that the good from my donations needs to be weighed against.
 Though when I started working on ads I set up Ad Manager ads at the bottom of each post, for practice.