Valve promised to crack down on gambling outfits that use Steam for commercial gain, and it's staying true to its word.
A letter from Valve general counsel Karl Quackenbush made the rounds on social media this morning (per Ars Technica). "Your commercial use of Steam accounts is unlicensed and in violation of the Steam Subscriber Agreement. You should immediately cease and desist further use of your Steam accounts for any commercial purpose."
Quackenbush went on to inform the recipients that they have 10 days to cease and desist. Should they fail to comply, Valve will pursue "all available remedies" including account termination.
The letter went out to 23 online gambling sites including CSGO Lounge and CSGO Lotto, two of the most well-known of the bunch. These and other sites have profited from Steam's marketplace by letting players parlay in-game items like weapon skins into more and/or better skins, which carry sellable value on sites like eBay.
Mailing out cease-and-desist letters will keep Valve's general counsel occupied, but fruitlessly, one could argue. Creating Steam accounts is a trivial matter: they're free. Valve may find itself forced to choose between playing whack-a-mole against sites that open alternate locations faster than attorneys can send letters, or taking sterner action to set an example to imitators.