Monopoly abuse can of course impact both suppliers as well as customers, but in this case it's probably more likely to only impact advertisers.
- As individuals we can switch to other search engines and browsers, so it's difficult to abuse a monopoly that way.
- However, as long as we keep using Google, advertisers might have no other option to get a reach this valuable. So Google could possibly exploit its position towards advertisers. (e.g. Favor its own ads over other ad networks).
Still looks like a net win for end users.