Tanning beds are unequivocally bad for you and should be avoided completely! Tanning beds are not safe and, in fact, they have been called one of the major public health
problems of our society. There is a very strong association between tanning beds and premature aging of the skin (wrinkles, sagging, drying of the skin) and the development of skin cancer.
Tanning beds are not just like lying out in the sun. The intensity of the light they deliver is stronger and more damaging that normal sunlight. Even if you do not burn while tanning and otherwise adhere to the guidelines suggested by the tanning company, you are still doing damage to your skin.
It is also not advisable to lie out in the sun for long periods of time in the summer. When you do so, you should be always applying sun screen. Even minor sun burns, when they are repeated, raise your risk both for skin cancer or for premature aging of the skin - unfortunately, there really is no 'safe' tanning alternative, whether tanning beds or natural sun light.
If you have more questions about this issue, feel free to talk either to your primary care doctor
or your dermatologist