Mormons don't shun like other religions, at least not anymore. Nowadays when someone leaves the Church he or she will likely still be welcome to come home to be with family and friends will still answer a disaffected friend's calls, but to say that everything stays the same would not be accurate for the vast majority of people who leave. Mormons handle dissidents with extreme care and expect former Mormons to agree to an awful lot of self-censure. It can make for some extremely uncomfortable encounters when family and friends are obviously concerned about casting their pearls before a swine such as yourself or when they're afraid that your opinions are aimed at corrupting and corroding their faith. It's not a pleasant feeling to have something you would like to say but don't dare say it for fear of offending people you love.
Mormons don't typically shun, but don't be surprised if they speak less frequently to you once you've left. Don't be surprised when old friends and acquaintances shy away and eventually disappear. It's only natural that removing a cornerstone of your relationship, if not the entire foundation of your relationship (as in the case of friends from church), would place some serious stress on both parties. The party who stays will, of course, be thinking "damn, I wish my friend would lighten up a bit and let the Spirit guide" while the party who has left is thinking "for fuck's sake, why can't they turn off the Church-installed chanting and think about this as though they were hearing it for the first time?!" How could a get-together between these parties possibly feel comfy and cozy? This is is just the natural result of growing apart, right?
Not really. Mormon leaders and Mormon scripture actually teach adherents to view those who give up Mormonism as sad, pitiful people, who are often consumed with bitterness and hatred. Apostates are cold and aggressive. They've adopted unhealthy lifestyles that drag them further down. They've been beguiled of the Devil and are too hard-hearted to accept the gift of Christ's Gospel. Mormons pray for those who leave the same way they pray for sick people.
Why should anyone belong to an organization that believes people who once believed but now think differently are mentally ill or possessed by the Devil? It's really weird. It's one of the reasons why Mormons don't dare think outside of Mormonism - it would be like having sex with someone who's saturated with venereal diseases - distasteful and dangerous! Most Mormons won't touch it. At least not without their 10' pole and their gloves on. It's not quite shunning.