Soros and Buffet have such an influence though their effect is likely to be considered beneficial by unbiased observers. Middlemen are a different story because most of them belong to the active subcategory. This means that they, on purpose, generate market inconsistencies, inefficiencies and problems only to solve them later at a cost extracted and paid to them, the perpetrators of the problem. Leaving ethical questions aside, this is a highly wasteful process. Middlemen use privileged information and access whereas speculators use information of a more public nature.
Speculators normally work within closely monitored, full disclosure, transparent markets.
Middlemen thrive of disinformation, misinformation and lack of information. Middlemen monopolize their information speculators share it, willingly or not. The more information becomes available to more users the greater the deterioration in the resources consumed by brokers of information. The same process will likely apply to middlemen of goods and services. We are likely to witness the death of the car dealer, the classical retail outlet, the music records shop.