Last I heard, more theists were turning to atheism/agnosticism than the other way around but I suppose this is all region-dependent. Due to the popular New Atheist movement, droves of people are now professing their atheism in the UK and other commonwealth countries. It has also been acknowledged that many atheists will report themselves as religious to avoid social stigma in their families and in places that are feverishly religious, such as the southern USA and the Middle East.
Certainly there are known former atheists that became religious, for example, notable Christian apologists, William Lane Craig and Kirk Cameron. Some come to religion via marriage - it helps if you outwardly share the same religion as your spouse and, in some cases, you have to be identified as a believer for the marriage to be sanctioned. The born-again Christian and other evangelical movements were able to reign in many non-practicing individuals who had previously been living out-of-control, aimless, hedonistic lifestyles.
It's the lifestyle of the religious that is perhaps most appealing for those who become practicing theists. The sense of community, social support, ritual, righteousness and the pride of affiliation all factor into the equation. Indeed, there are plenty of atheists who have joined Churches and Mosques for this very reason - not because they actually believe in the scriptures and dogma but rather as a means to fulfill their emotional and social needs.
The suggestion that atheists are those who reject religion so that they can live the easy free life is a complete fallacy. First of all, most atheists were raised in a religion and, in my experience, each struggled for some time to keep their comforting beliefs. Since most of the world is still clings to the inherited beliefs of their families, it's a difficult position to go against the grain. Ritual and spirituality have always been integral aspects of human life so they are not easy nor advisable to divorce oneself from. When one is no longer able to believe mystic explanations and commands, a psychological void needs to be filled. For some, it is via innocuous belief systems or practices that don't contradict reason. For example, many atheists, whether they practice Buddhism or not, meditate regularly. Similarly, former Muslims I know will continue to do their daily prayers as an alternate form of meditation. Then there are others still, like myself, who unable to believe ancient stories, scriptures and doctrines, continue to believe in God but as a deist.