[yish]

Typically you would sear the fish/beef/chicken before/after for texture, flavor and color. Beef for instance will come out grey on the outside and look unpleasant unless seared (inside is still bright red/pink though).

The bigger risk is the time that the food is left in the danger zone of above 50 degrees and below 125 degrees (don't quote me on those numbers, going off memory). Basically any bacteria present in food in that temp range will start reproducing quickly. I have heard 4 hours as the time limit acceptable to have food in that temp range before being considered unsafe.

[electromagnetic]

Beef is ideal to sear just before SVing, not only does it seal in the moisture, but the most dangerous bacteria on beef is on the surface, and just slapping the beef down in a very hot pan, flipping and removing is enough. This is why you can have a blue steak that is cold on the inside (not in many restaurants however) and cooked on the outside.

Searing your steak before cooking would likely aid in the hacked SV as a lack of vacuum sealing means some moisture may be lost, but searing prevents this. It also protects the average, less experienced, cook from giving themselves a wicked case of food poisoning.

[Snoddas]

Searing does not prevent any moisture loss. http://en.wikipedia.org/wiki/Searing