Stupid questions about retention

Hi all,I'm new to carrying and I've got some potentially stupid about retention holsters.1) How necessary are they, really, when carrying IWB? Let's assume I'm not going to be jumping over fences and doing flips and whatnot, and I'm not a cop where people may be trying to grab my gun from me.2) Having said that, a retention device is attractive to me because you never know, if I trip and fall I don't want the gun coming out. However, aren't they dangerous?Check out this guy shooting himself (despite being very practiced in his draw), seemingly because his index finger-activated release mechanism prompted him to curl his index finger in while drawing, and hitting the trigger.3) Are there other retention mechanisms other than an index finger button?Thanks! via /r/CCW http://ift.tt/1quyMTv