Can someone explain something to me about buy outs of other companies

I have unfortunately or fortunately had the luck of owning a couple of stocks that are in the process of getting bought - AB for one that is getting bought by InBev at $70/share but one could buy BUD for 63.00 today.  I understand the fear that the deal could not go down but how likely are those chances... 

 

But, if one doesn't mind having the capital invested until the end of the year would stop from someone from buying at 63.00 and waiting until it closes.

 

I guess the question is that the spread on some of these deals are huge right now - BUD is at 17% and BAC buying of MER is almost 14% - Dow's purchase of Rohm is 11%

 

Is the fear of the SLM et al. blows up by PE groups and just the general fear making these spreads or am I missing something.