Not necessarily when you factor in that you may need tens of thousands of accounts to suppress one popular site. - And in a profitable niche you're likely competing with multiple sites.

Keeping all those accounts active, cycling out dead accounts etc. could take quite an ongoing infrastructure investment.

Moreover google could give significantly more weight to accounts that look very real (i.e. actively using multiple google products for a long time) and thereby further devalue the botnet impact.

It's yet another arms race of course. But one with fairly good odds I would think.