I have a hazelnut/filbert tree in front of my house but every year the squirels take all of them before they're ready to eat. Does anyone know a safe method for preventing this theft of my nuts?

There is a lot of info on the web to help you. Some looks quite time consuming and expensive as does the following - You can squirrel-proof valuable trees by placing 2-foot wide metal bands around them, 6 feet off the ground. Trim overhanging branches to prevent access. To stop squirrels from stripping the bark off ornamental trees and shrubs, wrap trees with metal sheeting or protect them with squirrel baffles, as you would a
bird-feeder pole. Tree wrap keeps squirrels from gnawing on bark by keeping them out of the tree. Wrap all trees within branch-to-branch jumping distance. This method works well on trees near feeders or around your house. Prune trees near the house that give squirrels access to the roof. Remember to allow for tree growth when wrapping. If you have a continuous tree canopy that
allows squirrels easy movement, you will have to find another means of control.
Feeding is the easiest method to prevent squirrels from stripping tree bark. Scatter shelled or cob field corn on the ground near the trees or bird feeder or place it on a shallow feeding platform. Squirrels are fond of sunflower seeds and nuts, but nuts can get very expensive, especially as most end up
buried rather than eaten. Protect valuable crops by building a fence of 1 inch mesh wire. The fence should be at least 30 inches high and extend 6 inches below ground, with an additional 6 inches bent outward at a 90-degree angle to discourage burrowing. Set at least 2 electrified strands, one 2 to 6 inches above ground and the other at fence height. Set the strands about 3 inches away from the fence.

You may find that http://mgonline.com/articles/squirrel.aspx is a good site to check over

I think the best way to go is Police Protection. I found the following article at
http://www.lonelyplanet.com/scoop/archive.cfm?DPID=539 and region=asi

Thai riot police will wear specially modified groin protectors following a rash of testicle-grabbing incidents. Angry protesters have been increasingly targeting Bangkok's riot police in their most vulnerable areas and police Major-General Damrongsak Nilkhuha is the latest victim of what appears to be a series of testicle grabs. The Major-General was working with riot police at a rally of 300 sacked textile workers outside Prime Minister Thaksin Shinawatra's house when the incident occurred. A woman reportedly crossed the barricade, grabbed his testicles from behind and squeezed them very hard. The grabbing caused 'humiliating damage' to Major-General Damrongsak, and it seems other members of the police force were also pinched in their sensitive nether regions during this and other protests. In response, a Thai company has offered to donate a thousand groin protectors to the Bangkok riot police. The company, Nation Man Thailand, is a manufacturer of groin protectors for Thai boxers. Made from elastic and polyurethane, the protectors are designed to reduce the impact of a direct blow. The police force has accepted the donation, though they have asked for special modifications to make the devices appropriate for police usage. However, Friar Tuck has given some alternate ways that are very effective.

There also is an article called 'Black Market for Clean Pee.' It seems the Thai government, has decided one of the best ways to fight the country's methamphetamine problem is to give students mandatory urine tests. Compulsory urine tests will also be required of foreign laborers. Thus creating a large and lucrative market for piddle peddling entrepreneurs. It really is all quite interesting!! LOL!!

I, too, have a hazelnut tree and a good many squirrels. Squirrels are adorable rascals, but they do create problems. The humane, and preferred, solution is to trap them and send them on their way (but more will come, undoubtedly!). And why do mine leave that tree alone and go crazy for my walnut tree? Their little 'burying ritual' leaves me with a million walnut saplings every Spring. This is another of those questions where it boils down to how aggressive you want to be. I feed mine sunflower seeds regularly but generally yell at them daily. As for your nuts, well, that's a whole other issue.