Something has been bugging me about the Vegas marriages and even Lori and Chad's marriage, and what they say about motivations. Maybe someone can help me flesh it out.
I think the marriages may point much more heavily to money/legal motivation than to "cult cleansing"/must marry someone in the fold, or anything else religion-related. And, in turn, if the marriages were more money/legality motivated than religiously motivated, maybe the disappearance of the kids is less likely to be religiously-motivated, too. I don't know if that helps at all narrowing down where the kids could be, but at least it gives me more hope they are alive, not dead in some cult-mission-from-god-these-kids-are-dark-spirits scenario.
In LDS theology, a marriage--a legal, civil, piece-of-paper marriage--is an earthly thing "of man." A temple sealing is what is important and focused on. It's a saving ordinance, which means you can't get to (the highest degree of) heaven without it. A temple sealing for a live couple (as opposed to proxy sealings for the dead) is most often both a legal marriage and religious ordinance. The temple sealer is a legal officiant. But some couples are first married outside the temple in a regular wedding ceremony, and later are sealed in the temple. In that case, the sealing ceremony is just that: a sealing, not a marriage.
Now, we know Chad et. al. had one foot in the mainstream church and one foot in the fringe/possibly his own church. As such, maybe he holds no stock in the regular Mormon temple and the sealings there. But then you see a lot of these fringe groups performing their own marriages, and bypassing civil marriages--civil marriages aren't what "count" anyway.
But there is some reason(s) that this group of supposed anti-government religious fanatic cultists wanted government civil marriages. I can only think it's because they wanted some advantage(s) that civil marriages provide, and they obviously wanted them *quickly.* So, what advantages??? Community assets? Automatic beneficiary in case of death? Spousal privilege barring testifying against spouse (which has exceptions that vary from state to state)? Something else I'm not thinking of? Health insurance

?!?!? (I don't think anyone but MB's spouse is likely to have a company-sponsored plan.)
The other reason for a civil marriage is because it makes one look more above-board to one's children/family/friends. But then, it would be just as easy to lie and say a marriage had been performed out of state, even if it hadn't. I guess since we still don't have a record of the Daybell-Vallow marriage, that could still be the case. Also, if one is still holding to LDS standards, a marriage (civil or temple) takes having sex from the realm of grievous sin to "go for it" (sex outside of marriage is a sin). Or maybe they just *wanted* to actually be married, and since they couldn't go to the temple, they did Vegas (or Hawaii or wherever, for Chad and Lori). Chad and Lori may have been able to get married in the temple, actually, but not likely for Melanie, don't know about Zulema or Alex. Women can't be sealed to more than one person at a time (civil divorce doesn't dissolve a sealing), and you have to answer affirmatively to certain behavioral/belief standards to go in the temple.
Just my ramblings that I'm not feeling able to put to words. Does anyone get what I am trying to say? Why these quick civil marriages that don't hold religious weight?
All of the above is MOO.