The problems with Memory Sticks are
1. Memory Stick Pro Duo is considerably more expensive than SDHC with similar capacity.
2. Memory Stick is sold by Sony and Sandisk only. So there's less competition, and fewer low-price deals.
3. Sony recommends using these high speed Memory Stick Pro Duo models only:
Memory Stick PRO-HG
High Speed Memory Stick PRO
These high speed cards are not available in large capacities yet. I think 4GB is the maximum today. There are 8GB Duo cards on the market, but they are not the high speed models. For some reason, Sony doesn't recommend the new Mark II cards for use in the D50.
Sony's specs for D50 Memory Sticks is here
http://esupport.sony.com/perl/support-info.pl?&info_id=19Some people here have reported success using the slower Memory Stick Duo cards with the D50. There are several slower Memory Stick Duo models, so you have to be careful which you choose.
Flintstone