• An attacker has access to zero-day vulnerabilities to the software running on your device¹.
• You are storing non-Tor files on your device that can be used to build a profile against you. That or you are running OSX².
• That Flash and Java are horrible messes of software, and will break your security³.
• That Online tracking of your anonymous activities can later be used to connect your real identity with an anonymous session of tor usage. Deanonymization is a big research area but with rather little known results in the real world. Search data, social network profiles and large written texts have all been subject of deanonymization research.
• That Correlation attacks are practical if an attacker knows the entry node traffic and the exit node traffic. This is also a hot research subject, and the threat model can be created by for example reading the linked research on the tor blog⁴.
• Mixing you real identity with anonymous identity can cause harm.
• If you rent time at virtual hardware, the real hardware owners can see everything you do.
• An attack, presented in a 2013 research paper⁵, to verify if a hidden service is using a guard node owned by the attacker. It then assumes that a hidden service will randomly pick at least one of of 23 tor nodes with a probability of 90% if run under a period of 8 months for the cost of 60 USD per node per month.
I could not guess a threat model for "Your workstation must be a laptop". As a last line of defense, my workstation hard drive is equally easy to destroy with a hammer as my laptop. The cell phone advice is also quite bad - see SamReidHughes comment.
1: http://security.stackexchange.com/questions/40072/could-some...
2: https://research.torproject.org/techreports/tbb-forensic-ana...
3: https://www.torproject.org/docs/faq.html.en#UseTorWithJava and https://www.torproject.org/docs/faq.html.en#TBBFlash
4: https://blog.torproject.org/category/tags/entry-guards
5: http://www.ieee-security.org/TC/SP2013/papers/4977a080.pdf