Hi,
1. In terms of LinkedIn, here is a video that will help explain the power of LinkedIn: Linked Influence.
2. Myspace is still there for leverage, but I think the focus of it has moved towards music.
3. Photo sharing, I would recommend: Flickr and Photobucket.
4. I would definitely recommend Foursquare over Gowalla due to its massive popularity. And any features it may lack I am sure it will be developed within 6 months most likely.
5. I would skip the group texting, as this would be just one more thing to manage. I would have people just stick to communicating on Facebook and Twitter.
6. I would suggest Blogger and Wordpress.
7. I am not familiar with Fwix or Whatser.
8. Definitely go with Groupon, but you could certainly try Living Social for extra umpf!
9. Bump has multi phone support, I'd recommend that.
10. I would create offers for both Foursquare and Yelp if that's what the customers use. It would also create additional exposure for the business and helping them get people they would never normally have would make them happy.
11. Slideshare and Hubpages aren't apples to apples, but you should use both.
12. Use both Squidoo and Scribed.
Hope my opinion helps.