Before I read Breaking Dawn, I figured Jacob would either not show up completely or crash it like the volatile imbecile he is. Most of the time, I feel as if Jacob is always just looking out for himself. He doesn't care too much that Bella is more in love with Edward than she is with him. Jacob kept trying to force it anyway, by kissing her the first time, and then by putting her under duress into kissing him the second time. What a jerk! That's why I was leaning towards him crashing the wedding. It would be regardless of how Bella feels because Jacob just wants to make sure Edward is miserable for taking her away.
Jellycones
I'm not completely sure, but I really think he will crash it. And Bella can't really get mad at him either because 1) she invited him..as her best man. and 2) She really misses him.
Except towards the end of the book, Bella made sure he WASN'T on the guest list and Edward was the one to send the secret invitation. Though she is hurt because of Jacob's predicament, Bella realizes what she had to do but she can only be apologetic, not completely mind-altering as to choose Jacob instead of Edward.