We are all officially overpaying for data. Sprint and AT&T have already demonstrated they are willing to dangle huge amounts of wireless data (that will likely never be used) in front of potential customers, and now T-Mobile is hoping that the lure of vast amounts of data (which, again, will probably go unused) is enough to bring in new family plan customers. At the same time, the company has brought back its previously popular 4-for-$100 plan that may be the better deal for most people.

This morning, the little magenta wireless provider began touting a limited time offer of family share plans (at least two lines) with unlimited data for $100/month (plus all the phone charges, taxes, fees, and other nonsense).

After two lines, each additional line (up to 10 total) is $40 more. So a 4-line unlimited plan will cost you $180/month.

One nice thing about this offer — unlike the Sprint “cut your bills in half” promo — is that T-Mobile doesn’t require you to buy a new phone from them. So if you have a decent device that is compatible with the TMO network, you won’t have to splash out for a new one.

By that same token, if you’re looking for a new plan and want a new phone, you’ll have to pay full price through T-Mobile. Sure, it’s in monthly installments but it’s still hundreds of dollars more than you’d pay for the same device with a new contract through AT&T or Verizon.

Then there is also the question of whether or not you actually need an unlimited data plan. Most people only use around 2GB/month. This will likely increase as more people use their phones to stream bandwidth-heavy video, but many people also stream such content over WiFi networks that don’t impact their monthly data allotments.

So it’s in your best interest to do your due diligence and compare offers from other providers, as you might save money by choosing a family plan with a reasonable amount of data that you’ll actually use. Just make sure your family members don’t go over that limit because it could get ugly.

In fact, T-Mobile has resurrected its former 4-for-$100 offer, which gives users 10GB of 4G LTE data on four lines for $100/month. At 2.5 GB/month, most consumers’ data needs would be covered, and at $80/month less than the cost of the unlimited plan.

While we’re on the topic of T-Mobile, we’ve heard complaints this morning from people saying the T-Mobile site is acting up and emptying their shopping carts before they could finalize their order. Additionally, a number of people aren’t happy that the promotional pricing for either the unlimited data deal or the 4-for-$100 offer isn’t reflected at checkout. Instead, T-Mobile promises it will be “reflected on your bill.”

Given that T-Mobile is currently being sued by the Federal Trade Commission over alleged bad billing practices, you can understand why people are skeptical that they won’t be overcharged when their bill shows up — or that their rate will suddenly increase at some random point in the future.

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.