Not only conglomerates but anyone with the money and know-how. Example P&G proxy fight:
https://www.reuters.com/article/us-procter-gamble-trian-inve...
Neubecker said he has seen several ads on his Facebook feed that link to Trian’s “Revitalize P&G” website and to videos of Peltz and former P&G Chief Financial Officer Clayton Daley, who is advising Trian.
The video of Peltz features him sitting in Trian’s Park Avenue, New York City headquarters, discussing P&G’s future, gripping a Trian-labeled coffee mug that reads “Sales up, expenses down.”
In response, P&G has called upon more than a century of product marketing experience with its own “Vote Blue” campaign.
One YouTube video begins with an image of P&G’s blue logo and a banner proclaiming “Every Single Vote Matters!”. A narrator and series of slick images offer step-by-step instructions, ending by asking viewers to vote for the blue proxy card and to throw Trian’s white card in the recycling bin.
Trian won this fight.