What do you mean by "enough" backlinks? Enough for what?
See, with links, it's not so much a matter of
quantity as it is
quality.
Some sites simply don't have that much link value to pass. There's much more value in one link from a prominent page on, say, the New York Times' website than a thousand links from some crappy blog that nobody ever reads, much less links to.
That's the problem with most every one of the link acquisition tactics you've mentioned -- they're all relatively easy, which means the individual links will likely pass (at best) only a little link value. Meaning you'll have to get a
lot of them to equal the "oomph" you could get from maybe only one or two high-quality links.
Beyond that, if the search engines have decided a site is
too low-quality (spammy, engaging in black hat tactics, etc.), they may even have shut off its ability to pass link value entirely.
Unfortunately, there's no way to tell whether a site is allowed to pass link value, so you could end up wasting effort acquiring links from sites that either have no "juice" to pass in the first place, or that have "juice" but aren't allowed to pass it along.
Of course, the sites that have the ability to pass along a lot of link value usually have that ability and value because they're high-quality sites... one aspect of which is that they're generally careful about who they link out to. Meaning that it's harder to get links from them.
That's the paradox of linking: the easy links usually aren't worth that much, and the links that are worth something are often hard to get. Fortunately, when it comes to high-value links, you generally don't need zillions of them.
Have you considered finding complimentary (not competitive) businesses to your clients and contacting them directly to see if they'd be interested in either a link exchange or some other barter arrangement? Perhaps there would be some local businesses in the same town as your client who might be interested in some cross-promoting? Links from other reputable businesses will usually be more valuable both for driving quality traffic and for search optimization.
My
--Torka
Which Of These Get The Most Backlinks?
