A couple of points not yet raised
This topic interests me because I handle all the memberships for my club (BSCC), so I am in frequent communications with MTBA about membership.
Most members I have spoken to about the turn around times for cards (when the online system is used) is between 1 to 2 weeks. However personally my card took 2 months to arrive this year, but that was because there was a delay in MTBA physically receiving stationary for the paper cards. It seems that in Jan-2011 they were working through the last of the plastic cards and once they ran out they had to wait until the paper cards arrived, which wasn't until March.
I only took over the role of BSCC membership officer in Jan-2011, previously there were huge delays with paper forms, but it turned out that most of that was as a result of my club not MTBA.
Currently my only problem is with value adds memberships. It is a 'feature' of the online system that when a member joins MTBA as a CA value add, the rider's associated club is set to CA, which means according to MTBA that rider is not a member of my club. It is not hard to get this changed, I just email MTBA and they fix it. The problem is knowing that a member has joined the club...
I suppose what I am saying, is there are lots of different reasons for a membership card to be delay, it just depends on the individual situation, the time of year, the backlog at MTBA etc. And while I agree the current MTBA online system could be better, its not the worst one I have seen.