I agree with the comments from BT and roadwarrior about Target. Sure, Target would pull in customers from all over the city and possibly hurt some of the mom-and-pops from far-flung places - but this area of Market (and the surrounding neighborhood) isn't exactly chock full of mom-and-pops that would be hurt by a Target. You can pretty much split the retail spaces in the area into these categories:
1. Boarded up storefronts
2. Restaurants - which would clearly benefit from more traffic in the area
3. Chain stores like Radio Shack - which seem to do just fine next to Targets in suburbia
4. Porn shops - I haven't really checked at Target, but I don't believe they typically have a giant porn section or viewing booths - could be wrong though
I just don't really see the downside - we're not talking about putting a Target on Fillmore or Clement or in North Beach or Polk or Chestnut or Irving or any one of the other mom-and-pop neighborhood retail streets.