Protecting Your ROI in the Age of AI-Driven Paid Media

$63 billion was wasted on invalid traffic globally in 2025. And now in platforms are asking advertisers to hand over more control than ever, with AI now making bidding, budgeting and targeting decisions that used to sit solely with the marketer.

In our latest Mediaworks Masterclass, COO David Norris sat down with Paid Media Director James Johnstone to unpack Google's upcoming smart bidding update, what it means for your campaigns and how to protect ROI in a world where the platforms are taking control.

What's Changing on 17th August

On 17th August, Google rolls out a significant change to how smart bidding treats target CPA and target ROAS campaigns. While the specifics are technical, the practical impact is simple: campaigns that previously delivered below your target will now spend up to it.

Under the old algorithm, a campaign with a £10 target CPA could actually sit at £5, because Google only chased search terms with strong conversion signals behind them. The new approach is far more aggressive. It expands the scope of queries your campaign can appear for, spends to the budget limit and pushes your actual CPA towards your target.

Why is Google doing it? More queries mean more data, and more data means a better trained AI. That's good for Google. But if you leave your campaigns untouched, there's a chance you'll artificially inflate your own costs overnight.

64% of marketers don’t fully trust AI to manage their paid media budgets

During the session, the majority of attendees said they don’t fully trust the in-platform AI and very few were comfortable handing over complete control.

That’s a sensible position, particularly given the direction of travel. Google is giving AI increasing responsibility for bidding, targeting, creative optimisation and campaign management. Meaning that successful campaign activity will come from knowing when to trust the machine, when to challenge it and, most importantly, when to step in. As AI takes on more of the execution, oversight becomes even more important.

What Still Matters

The fundamentals haven't changed, and effective paid media in an automated world still comes down to three core pillars.

Data and signal quality

The quality of your data and the strength of the signals you feed the platforms is what guides the algorithm. Enhanced conversion tracking, server side tracking and Conversions API on Meta aren't nice to haves anymore. Without those foundations in place, you can't capitalise on any of the advancements coming down the line.

Value based bidding

This is the bridge between your data and your commercial goals. It means building a hierarchy of conversion actions that reflects genuine commercial value, so the platform is optimising towards the outcomes that actually matter to your business rather than treating every conversion as equal.

Commercial objectives, not platform metrics

There are more soft vanity metrics available in platform than ever before, and it's easy to optimise towards something that looks good in a dashboard but delivers nothing to the bottom line. If platform performance is increasing but your commercials aren't moving with it, that's something worth investigating.

The new rule underpinning all of this is that you're not managing campaigns anymore. You're managing an AI system which means less obsessing over individual CPCs and more focus on governance: are you appearing for the right terms, is the system optimising in the right direction and is lead quality holding up?

If your team wants help putting those measures in place, Mediaworks can help you build paid media activity that takes the benefits of automation without surrendering your ROI to it.

What to Do Before 17th August

The good news is that protecting yourself is straightforward if you act deliberately.

What that means in practice:

• Review every target CPA and target ROAS campaign now and record your current baselines, so you can measure pre versus post

• Lower targets on campaigns you want to keep efficient. The simplest fix is resetting your target CPA to whatever you're actually achieving today

• Consider changing bid strategy where the current one no longer aligns with your commercial goals

• Accept the shift where it makes sense. Niche campaigns may benefit from expansion, but globally targeted campaigns achieving below target are most at risk of spending into less efficient markets

• Put a recurring review in the calendar. This won't be the last update, and set and forget has never been a genuine strategy

• Watch invalid traffic as you enable broader features. Campaigns with AI Max activated are seeing around 35% more invalid traffic, though if conversion quality holds up, performance should stay the priority metric

To help you see how your own digital performance compares, we're offering a FREE Digital Performance Audit through MX, the Mediaworks measure of experience. The audit benchmarks your digital activity against your peer set across brand, reach, authority, technical and engagement, drawing on a range of unique data points to show exactly where your strengths sit.

You'll receive a clear view of how you compare against your competitors, along with the priority opportunities to improve visibility, engagement and commercial performance.

You can request yours here