jquery autocomplete this.source is not a function error

Answer is that the first parameter of the autocomplete should be an object containing the "source" property. This works

var fakedata = ['test1','test2','test3','test4','ietsanders'];
$("#omschrijving").autocomplete({source:fakedata});

If you were trying to use autocomplete from http://www.devbridge.com/projects/autocomplete/jquery/#demo, it now collides with the autocomplete method in jQuery UI. I had the same problem and later noticed that I could just use the jQuery UI implementation.

(NOTE: It appears that this page's documentation is wrong: http://docs.jquery.com/Plugins/Autocomplete#Setup)