Sure it is, memory has come down a lot. I would go higher than a class 4 though. For 20 bucks, you can get a class 6 Transcend 8gig.
[ame="http://www.amazon.com/gp/offer-listing/B000P9ZBFA/ref=dp_olp_new?ie=UTF8&condition=new"]Amazon.com: Used and New: Transcend 8 GB Class 6 SDHC Flash Memory Card TS8GSDHC6[/ame]
Or for 34 you can get a Sandisk Extreme III 8gig Class 6
[ame]http://www.amazon.com/Sandisk-EXTREME-Class-SDSDX3-8192-Package/dp/B0018M256G/ref=sr_1_7?s=electronics&ie=UTF8&qid=1276315102&sr=1-7[/ame]