Aiden and Nathan each have a PC to "use".
Aiden is 4 and this is his first one that is his to use. It's an old cracked laptop set up to an external monitor, keyboard and mouse. He has Office installed, a bunch of kids games (timez attack, Jumpstart for various grades, Reader Rabbit for various grades etc). All his favourite websites are bookmarked, and his favourite learning sites (Kahn, Mathletics etc) are shortcut to the desktop. He can google and we have strict filters and kidsafe software on his PC. He knows that he needs to check with us what subjects he is googling first (I tell him its to make sure the spelling is correct). You tube is fun, but when they are on it (normally Aiden browses and nathan watches) I am always in earshot.
Nathan (2y9mo) works on our server - and has learnt not to delete, move or do anything without asking. Again, he has full internet on there, but only accesses his sites. (cbeebies.co.uk, topmarks, and disney junior being the main ones for him.) he also has reader rabbit and Jumpstart on there.
No PC's allowed in the rooms is already a family rule in place. so they know already that it will not ever happen.
They will both get their own proper PC's/laptops when they are older and using it for things that require more processing power than the fixer-uppers they currently enjoy.
They both still prefer working on my laptop though...
No computer programmers in our house (well, I did take BASIC in high school!), but my DS is nearly as technologically advanced as we are, so we had similar thoughts about his ability to get around any controls we had. We also had a few viral attacks on our PC in the last few years, so DS is also extremely careful to not click on anything that pops up (even though we now have a Mac to avoid some of our virus issues). I do like that we have had many discussions about what's appropriate on the internet. We had very interesting talks about why people would create viruses, etc.