I think trend is a loaded term.
The internet is a place for people to 'try out' who they are and who they want to be in many different ways. Do I think there is a 'trend' for people to identify as trans? Quite possibly. Adolescence is a time of figuring out your identity, being confused, and the brain is still developing. Even though I think the classic statistics about transsexualism understates how prevalent it is, I am still highly suspicious that as many young people who claim to be trans - and probably believe that they are - actually *are* trans & will be as adults.
When I was growing up (yeah, this makes me sound old), there wasn't a "trend" of being emo, and there wasn't a "trend" of young people cutting themselves. Do I think that people didn't self-harm? I'm sure some did, but I do think that some disordered behaviors allow people to feed on one another, get ideas, and almost 'compete' (I'm thinking of eating disorders or other body dysmoprhic disorders), which means that technology & communication has probably made "trends" out of more disordered acts. While I view actual "gender identity disorder" as a medical condition and not a disorder, that doesn't mean that some of the people who THINK they have GID aren't actually disordered or confused. My hope is that advances in neuroscience may hold some keys and answers to figuring out what the condition known as GID really is and how it manifests itself, though I'm sure we're still quite a number of years away from having much to rely on.
That said: No one has any evidence about how many of the young FTMs out there (whether posting on youtube or forums or blogging) are *actually* transitioning. It really isn't so easy for teens under the age of 18 to just start HRT or get surgery. I don't think it is actually a "trend" until we have proof of actual transitions, rather than trans identification. Adolescents cutting their hair and calling themselves boy names or bro or binding their chests and even calling themselves "FTM" is definitely a "trend" - but it doesn't mean there is actually a trend of people who are and will ultimately transition to live lives as men.
I do fear that if transitioning were easier, especially for young teens, there would be a lot more de-transitioning going on, and it ultimately would harm the abilities of people who really do need to transition to do so. And I do find it difficult finding the right balance between supporting youth and teens - whether they are trans or not - and being open to the fact that not everyone who thinks he or she is trans really is or will be in the future.