This is actually a surprisingly difficult question to answer. If you had asked specifically about tobacco, you'd be correct. But, nicotine itself may not be as addictive as tobacco products are.
Remember that tobacco contains many other compounds that influence how the body metabolizes things (MAOI's and such). Here's a link with some citations: http://www.healthnz.co.nz/Addiction_TobNic.htm
EDIT: My personal anecdote is that I tried vaping when the first 901 ecigs started to hit the US market: the idea was twofold. I wanted to assess whether there was any cognitive benefit in using nicotine through a cleaner delivery system and I also wanted to get my dad to quit smoking cigarettes. Both goals were failures, I found it too difficult to dose reliably using this method and the side effects weren't worth it to me. I did not find myself addicted after around a month of use.
Remember that tobacco contains many other compounds that influence how the body metabolizes things (MAOI's and such). Here's a link with some citations: http://www.healthnz.co.nz/Addiction_TobNic.htm
EDIT: My personal anecdote is that I tried vaping when the first 901 ecigs started to hit the US market: the idea was twofold. I wanted to assess whether there was any cognitive benefit in using nicotine through a cleaner delivery system and I also wanted to get my dad to quit smoking cigarettes. Both goals were failures, I found it too difficult to dose reliably using this method and the side effects weren't worth it to me. I did not find myself addicted after around a month of use.