How old was the Wyeast package? If it was several months old, it may just be that it took a while for the yeast to get to a decent population before you saw signs of fermentation.
The real test, though, is to take a specific gravity reading to see if fermentation has started and how much has been fermented.
The brew is not in danger unless fermentation has not started, but that's probably not likely. You could pitch another package of yeast, but it may not be necessary. It wouldn't hurt the flavor.
There are many factors affecting how fast fermentation starts, most importantly the health of the yeast you pitch. If the Wyeast package was old, then that would be the primary reason for a slow start to fermentation.
Again, I suggest taking a specific gravity reading to see where you really are with the fermentation, then taking (or not taking) your next step based on that information.
On Deck: Jamil's Vanilla Robust Porter
Fermenting: Orange Blossom Mead
Kegs: Element 56 Pale Ale, Ron's Belgian Blonde, Summer'n Saison, Furloughktoberfest '09, Grateful Pale Ale, Sam Adams Cream Stout Clone, EdWort's Apfelwein