Erowid
In case Flakka's nickname "$5 insanity" doesn't tell you all you need to know about the drug, there are reviews on Erowid, the Yelp of drug use out of San Francisco. Erowid.org

In case news of people stripping naked and running in traffic, trying to have sex with trees or needing to be restrained by five burly police officers doesn't tell you what an experience with the synthetic street drug Flakka would be like, there's always user reviews on Erowid.

Founded in 1995 in San Francisco, Erowid's mission is to document "the complex relationship between humans and psychoactives." It got nonprofit status in 2005, and exists thanks to donations, as no ads run on the site. Erowid even runs EcstasyData, a pill-testing program co-sponsored by DanceSafe and IsomerDesign that collects, reviews, manages, and publishes lab pill testing results submitted by users in order to monitor the quality of the street drug MDMA or Ecstasy.

If you've ever wanted to know what it was like to take Flakka, check out the full reviews on Erowid's "Experience Vault," excerpts below, with titles that reflect the writers' wildly disparate experiences -- "A Completely Misunderstood Compound" and "The Devil in Crystal Form" are just two examples.

"I loved the feeling, I was instantly ready to go into everything and felt like I did with my previous methylphenidate come-up." But then, "Days were ruined, I would begin working on my daily errand, and just blow through the first 1 -2 hours, and then spend the next 7-8 feeling completely hopeless, unhappy, and incoherent…So by day 10, I was redosing every 2 hours just to maintain myself. "

"After breathing out the first 4 mg hit I immediately feel strong rush. It started with tingling and shivering over the body. My breathing got very slow and deep and my penis got erect. My limbs were moving involuntary in delightful manner. Rush lasted about 10 minutes and left me with racing thoughts and strong compulsion to redose."

"It dissolved rather quickly, numbing my tongue in a fashion similar to cocaine but with diminished potency...From here I continued to walk around the flea market, attempting to keep my spit in my mouth while unfortunately swallowing most due to my entire mouth eventually getting numb."

"She told us she didn't feel much of anything the first 15 minutes. Then a slow and subtle force of productivity and energy began to take hold of her. She said it didn't feel like Adderall or Ritalin but something only remotely similar. Her brain was firing on 800 cylinders! She felt like a genius and started to handle some of the chore things around the house that are usually avoided."

"I redosed at the 30 minute mark. Another 2-5mg insufflated (snorted). A little more euphoria and slight sexual urges but nowhere near MDPV, and the rapid heart rate was so bad I couldn't enjoy the little positive effects this drug has."

"I went from being responsible and happy, to a strung out mess CHEWING HOLES in my tongue, and getting severe facial ticks."

"This drug is illegal, and one of the few I fully 100% understand why. I lost 13 pounds in 20 days, lost friends, and even ruined 2 major class projects."

"The stuff lasts for quite some time...The only problem is that the high of it, the productive, brain cells firing on all cylinders, everything is awesome phase beings to die after 2-2.5 or so hours and then one is left with a still racing heart and most likely some insomnia to go with the complete lack of appetite and dehydration."