Here's something none ever talks about that I always thought about when it comes to the whole living on other planets thing. HUMANS. People always forget how fucked up mankind is. We mess up EVERYTHING. It probably wouldn't be too much of a stretch to say they we are one of the worst things to ever happen to the earth.
Going to another planet does not change that, if anything it just makes it much worse.
Think of all the crime, violence, prejudice and general hatred that is all over this planet. Now for all the failing that governments, military, law enforcement etc do, they do at least keep these issues at a much lower rate than what they would be otherwise due to enforcing punishments on people(somewhat) The only reason they can do that is due to having enough numbers and force to keep people in line. If law enforcement stopped arresting people for any crime they committed for one week...try and imagine what would happen during that week.
Now think about certain countries in this world that are practically lawless right now, or are ruled by cruel dictators. Now imagine that but as an entire freaking planet.
I have no illusions about human nature yes there is good in us, but there is a shitload of bad as well, eventually after the population got large enough these things would happen all over again only worse because there would be a significant lack of individuals that could enforce law or justice or whatever. And unlike flying from one country to another which is doable, you can bet governments wont be sending military personnel on a 7month trip to mars on peace missions. Same for regular law enforcement.
Maybe if these were qualified scientist this problem would be postponed but since technically anyone can apply, even with all the screening they do you have no idea what type of unstable mofo's are leaving earth with you.
Now of course what I'm saying wouldn't be all that valid if this was just a trip but since they're planning to live there permanently...hell no. This is just one issue. Other people in the thread have already touched on others.
In theory the idea sounds awesome. In actuality, if you dont die on the way there(very possible), and if you manage to land safely(you might not)...you probably wont like it all that much, but by then your stuck there sooooo sucks to be you.