Since upgrading to Tiger, my 12" 1GHz PowerBook has been running exceedingly hot, with the fans going flat out all the time. Foolishly, I assumed this to be a bug in Tiger that would be fixed in a later release; one exhausted battery and a number of updates later, there was no change and I decided I better investigate the problem…
Five minutes with
top -o cpu revealed that a process by the name of 'VShieldCheck' was permanently using at least 70% of the processor. Now, I've always been fairly sceptical of anti-virus software but, I thought on the Mac things might be different. Alas, it appears that the OS X offerings are as mediocre as those for Windows--purging my system of Virex has returned it to it's normal pre-Tiger performance!
It would be refreshing to see anti-virus companies spend more effort on writing a decent product and less on convincing the customer that they are at risk. Currently they seem to be focusing much more on the mobile market--another area in which they seem to be determined to talk-up risks, persuading users to buy software which adversely affects their experience.