If you really had your doubts about the bride or groom, you're a little late to express those concerns. Revealing them during the most expensive party the couple will ever host isn't the right time. You're at the reception to celebrate their decision to spend the rest of their lives together. Toast the commitment they've made to each other. The ceremony is over, the papers are signed, and it's a done deal! As someone who's esteemed enough to give a speech at your friend's wedding, your job is to be supportive -- no matter what your opinion.