Think of it this way: both artwork and marcom are concerned with the appearance of Mageia. It's all about how we present ourselves to the world. Whether it's a shiny desktop, eye catching posters or good content on podcasts. It all boils down to the same thing: how we look to the outside world.
One of main problems we have with this is good communication. It's not just this one project where the two teams need to work together, but it's many projects. Thinking back for a few seconds I recall the booth setup for FOSDEM, the posters, the disc covers and a few other projects where both teams needed to work together.
Aside from the lack of cooperation within the team, there was bad communication between teams. Efforts have been made in the past to try and amplify the cooperation, by staggering IRC meetings, by having people sign up for both mailing lists... but they never worked well. Most recently when we tried to collaborate we had many double posts on both lists, many redundant threads and many people being left out of the loop. Why? Because we were trying to communicate across two different lists and more or less the same people.
Now, to clarify: the proposal isn't to merge the actual teams, just the communication channels. There will be (under the new proposal) one mailing list and one IRC channel. But essentially both teams will function as before. Each team will have one leader and one council representative (probably the same person for each team) and one deputy. This way both teams can function as a single unit when it comes to cross-communication and idea sharing (which happens a lot), but each team retains its autonomy.