I've been on Capcal's reward scheme for about 18 months. The maximum payout I've had has been about US$1 a month, and in recent months 0.00 Over 18 months I've probably received about US$10 from them!
My firewall tells me that they access my PC for less than a second at a time. I've had no problems with their system, especially as the PC has to be on line 24/7.
I've found that filling in survey reports brings better rewards than CapCal. My "pocket money" from these - sometime paid in vouchers exchangeable in local shops, sometimes by cheque, sometimes with Amazon credits, runs at about UK£10 - £15 a month. There's no way I'd ever reach figures like that with CapCal, so, seeing as Dec 2004 looks like being another 0.00 month with them, I intend "pulling the plug" on them after Christmas.
Vic