My theory on what Tom and Katie got married
I think the reason Tom and Katie got married when they did was mostly about money. They saw first hand how Scheana got a $100K wedding that was mostly paid for my bravo and how the things like flowers, the venue, etc were given to them for free.
They are both decently smart people, so they know that the show isn't going to last for ever. If they got married 3 or 4 years from now, it is likely the show won't be on anymore or that Tom and Katie re no longer cast members. Therefore, to get a nice wedding basically for free could be now or never.
I think they both could see themselves marrying each other at some point, just not now. So they took a risk and got married despite the red flags so incase the marriage works out, they will have had the wedding of Katie dreams that they barely had to pay anything for.
BOOM! bazooka joe. -Randy Barry of The Real World: San Diego