We still have trust in Alexa statistics graphs ?

I did notice that many graphs statistics from Alexa website are decreasing a lot , even bhw website graphs shows a big decrease , Google Penguin algorithm can be the problem here ? or they just have problems with their statistic technologies ?
Did anyone notice this ?

Well if you have niche site like Wordpress blog than definintely yes.. Alexa stats and ranking is important for you and the advertisers..

Yes , true , for small websites Alexa graphs have no value