Rental shopping carts for website: are they worth it?

What’s the deal with paying someone else to run my shopping cart (my sales being in excess of 300 items)?

I’m pretty Web-savvy, but forms and cgis dealing with encrytion/security are pretty much too complicated and failure-prone (mainly by my ineptitude) to do it myself.

I’ve seen a million ads for these services but a Google search for “best shopping cart system” turns up about 267,543 items.

Are these places fly-by-night operations who fly to Brazil with your millions, leaving you holding the bag?