I don't know if this is the best place to ask this, but I've been reading about an interesting cryptocurrency called IOTA which doesn't use a blockchain exactly but instead uses a directed acyclic graph. https://www.iotatoken.com/IOTA_Whitepaper.pdf

There also are no dedicated miners, but instead you have to validate other transactions in order to make transactions. My question is the following:

If there are no dedicated miners, couldn't you get 51% of the computing power simply by making 51% of the transactions? And if so, isn't this a really big problem for the security of it?