15/15 or 30/30 is, IMHO, not enough.
FlyerTalk is a FORUM, which means two way communication; and about learning the ropes as well as helping to teach others what we are taught. The post minimums (and 90/90 is not unreasonable) means that your past posts can be checked for content to see if a user has actually put any effort into learning how to do anything, and if they have put some effort into helping others with passing on the knowledge they have gained.
Those that are just lurking around to try to grab some low hanging fruit and expecting to have their hand held all the way through the process are not the ones I understand the forum as a whole is looking for.
FT has become too much of "newbie here and can you walk me through exactly how to get that great mistake fare?", and "how do I earn 100,000 miles in 1 week?", and "please re-type and explain everything I want to know yet again because I am too lazy to bother reading the sticky threads at the top of each forum".
Yeah, I did manage to accumulate a million miles within 16 months after finding FlyerTalk, but I also put a lot of effort into learning the techniques and using that to find and use the opportunities; and I was posting help to others within two months (after first MR with IRROPS disrupting my first positioning flight, requiring quite a bit of phone work with CS to adjust the six back-to-back RTs to score AA's FLY3 bonuses, but I had the alternatives in hand so I was very prepared and it went quite smoothly; and I even attended an FT-do in the middle of it!).
Steve