Vacuum cleaners can cause a lot of static, but a single static jolt, while it may cause damage to the componants, may not always cause an obvious fault. There are millions of transistors on a modern CPU, and millions more in every gig of memory.
A single 'failed' transistor may not cause the computer to stop booting, but it could cause small errors to crop up, random windows crashing, many people just blame microsoft on their bad programming, its just as likely to be a minor hardware fault.
Sometimes the static discharge wont even do that much damage, it may just weaken a componant reducing its lifespan, or reduce a good overclocking part to being just 'ordinary'. But then if you have upgradeitis like I do, then the average computer part would be replaced before it actually broke down.
On the whole, using a vacuum cleaner on an open PC, or any electronic circuit boards is a very bad idea, a compressed air duster is the more appropriate way to clean them.