Both sides haven't done enough studies regarding this. However, it's already a widely and accepted fact that nicotine is dangerous.

It might be true that the government wouldn't want to lose side of income with the resurgence of e-cig, (come on, who would want to lose some money all of a sudden). However it's also worrisome that like the conventional cigarettes, 'non-approved' ciggies (i.e., smuggled) could contain 'alien' substances (even more so than the already dangerous substances in the controlled ciggies). The same could be applied to e-cig.

So to me, the call for controlling e-cig has two notions; one to control the possibly adverse effects from 'non-approved' e-cigs, and also not to lose money and support from tobacco manufacturers.