noctropolis -
+1 Yes you want to have a good mix of follow/nofollow.
If you don't have webmaster tools setup yet for the account, make sure and get than done. As you will then be able to see if you've had a manual penalty given to you from Google. If you don't have WT ready yet, a quick google search for site:yoururl.com will show how many pages Google has in it's database. It won't show if they are getting any search results, but if your site has been spidered, it should have pages that show up with that search, if it doesn't then something is wrong
The other thing I would mention that you need to be wary of, I see a lot of LS exchanges with money anchors only. For instance with
18 to 21 year old naked teens I try and do a 1/3 - 1/3 - 1/3 with 1/3 being
18 to 21 year old naked teens as the anchor, 1/3 being "Click Here", "Get more here", and the other 1/3 being long tail searches I'm targeting. "Shaved Wet Pussies" "Petite Naked Girl Videos" always try to get 3 to 5 words in the anchor. Having something like "free teens" or "naked teens" will most likely red flag you with Google!
Another aspect that will come into play with the SEO algorithm is the way you are linked. Content rich sites that get lot's of Google love, have links coming into all area's of the site, not just the front end
So you need to make sure that when your buying or exchanging links to help with SEO, that you are doing the same thing
Find adult boards that allow you to post your URL, mostly they will be "no follow" as boards don't want to give up any link juice, so you can balance out your follow/nofollow with comments/guest blogs/message boards, like adentio99 suggest, if you keep it in the 70/30 ratio, you should be good as gold.
As for your ?, there are a number of things that can make Google penalize you, yes if your link ratios are out of wack, and look like the thousands of other guys trying to play the google game, then yes you might very well get caught in a manual de-index
I think the very best advice I ever got about SEO was from a google tech on a board somewhere. His advice was to not think about what Google wants, but what does the surfer desire when he/she is on your site? What will make them stay around, and explore everything that you have to offer. Craft everything that you do, based on that, and you will get lot's of love from Google, try and fool the system, and they will end up slapping you with a penalty!