You have a couple of options available to you - and some thoughts before you continue.
Your first thoughts should be: do I really want to blow away my logs - what happens if I have to debug an error? What about if I get cracked back and want to see how they got in? Will I be doing anything illegal at all to justify blowing away my logs?
Especially if you are doing this professionally, keeping logs is essential for proof later on. If you are not, then you are either doing things illegal (in which case we can't help you) or you are being overly paranoid for no reason (in which case we can't help you - but I can recommend a good psych if you are in the .au region :P).
There is a third option which will probably pertain to you. I run my BT install on an Asus with internal SSD. It's lightning fast but I'd rather not have burn out too fast, so my /var/log directory is a separate partition created tmpfs (check the BT3 installation process for how to do this - I imagine the same will work for BT4 but I haven't migrated my portable to it yet). I make sure I rsync my logfiles to an external USB device during tests to be sure I have the files backed up and for reliability purposes, but when I'm just mucking around with my system, there is no need for this.
That might be your best option - other options include linking certain files to /dev/null ( rm /var/log/message && ln -s /dev/null /var/log/messages ) or using wiper programs.
If you are doing illegal stuff, I retract all previous statements and hope you get caught for appealing to my weaker moment this early in the morning.