I fold AK to pre-flop 3bets all the time at NL50.
<font class="small">Code:</font><hr /><pre>
equity win tie pots won pots tied
Hand 0: 42.870% 30.56% 12.31% 18835139 7591111.50 { AcKd }
Hand 1: 57.130% 44.82% 12.31% 27625582 7591111.50 { TT+, AQs+, AKo }
</pre><hr />
I shove vs. short stacks or once I have identified an opponent as a light 3bettor. I need more than 30 hands for that usually.