TheStreet's Jim Cramer says Athenahealth and Twitter are both potentially overvalued and Facebook could be undervalued. Cramer says he has been very suspicious of cloud companies since March. Cramer also says he thinks Twitter may go to $29 a share because it trades on metrics like average monthly users and number of tweets sent. On the other hand, Cramer believes Twitter has "genuine" earnings and has a "roadmap." Cramer believes the social networking site could earn $2-$2.50 a share in 2015.