HasselbeckA few thoughts:
Hasselbeck would fit in well with the 49ers. He knows the NFC West, obviously, and he's close to one of the 49ers' new coaches, Bobby Engram, from their years playing together with Seattle. Hasselbeck would benefit from the relatively strong ground game in San Francisco. He could stay on the West Coast, traveling easily between Seattle and the Bay Area. For him, this might be the next-best thing to staying in Seattle.
Don't discount the role agents play. As Matt Maiocco pointed out, Young has ties to Hasselbeck's agent, David Dunn. Agents like to create markets for their clients. Sometimes they like to create the impressions of markets for their clients. Having the 49ers mentioned as a possibility for Hasselbeck creates a little buzz. Dunn has also worked with 49ers coach Jim Harbaugh and general manager Trent Baalke, with some reports suggesting Dunn has represented them. Are Dunn and the 49ers messing with Seattle? It's tough to say, but a fun thought.
This would be bad for Alex Smith. Smith could not beat out Shaun Hill or J.T. O'Sullivan in previous camps. He's put up better numbers than Hasselbeck over the past couple seasons, but would Smith beat out Hasselbeck in an honest competition? The smart money says probably not.
This would be good for the 49ers. They need quarterback depth. Smith has had injury problems. Rookie Colin Kaepernick could need time to develop. Between Smith and Hasselbeck, the 49ers would get through the season with a smart, experienced player behind center. Hasselbeck's résumé would enhance the position.
The Seahawks weren't interested in signing Hasselbeck to a deal that would have given him security beyond one season. Their reported interest in Tarvaris Jackson suggests the team could be ready to move on without Hasselbeck. I wouldn't rule out a return to Seattle, but if the 49ers are interested, Hasselbeck would be wise to listen.